How to Diagnose and Repair Your Air Conditioner (A/C) Capacitor - Dengarden - Home and Garden
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How to Diagnose and Repair Your Air Conditioner (A/C) Capacitor

Author:

Dan has been in the HVAC industry for 23 years with experience ranging from installation and service to sales and distribution.

What's Wrong With Your Air Conditioner?

A capacitor usually resembles a tin can or 9-volt battery.

A capacitor usually resembles a tin can or 9-volt battery.

Capacitors Are a Common Cause of Air Conditioning Breakdowns

So it's a hot day in the summer sun. The family is coming over this weekend and you're very busy making all the necessary arrangements, when suddenly the A/C quits working. Perfect timing, right?

Well, before you call the local HVAC technician to come fix the unit and re-allocate the money you were going to spend on burgers, take a quick look. Perhaps you're about to luck out by making a simple repair that will only cost you a few dollars and take very little time. It's also helpful to find out whether your air conditioner is still under warranty, in case you want to replace it later on.

If you need to fix it right away, you won't need any special tools, and you may not have to rearrange your entire day. Just a few minutes, a couple of tools you likely have around the house, and these instructions could save you a significant amount of money while keeping your family gathering right on track.

Quick Overview: How to Replace an A/C Capacitor Yourself

See below for more detailed information and pictures.

StepDetail

1. Turn off the power to the unit at the disconnect or breaker panel.

Do not proceed if you do not know how to do this.

2. Find and inspect the capacitor.

Remove the service panel, locate the start capacitor, and check to see if it's mishapen.

3. Discharge the power of the capacitor.

Be very careful in this step — watch the video below for details.

4. Dismount the old capacitor.

It should be simple to unscrew the metal band holding it in.

5. Note down how the wires connect.

Do this before you remove them!

6. Disconnect the wires.

You can remove them with needle-nosed pliers.

7. Choose a replacement.

Know the micro-farads (μF) and the voltage rating, or the make and model of A/C

8. Buy a replacement and attach.

Check your local contractor supply store.

What Is a Capacitor?

Capacitors are small cylindrical objects that store energy. They either send a jolt to start a motor or send jolts to keep a motor running. They work with the compressor, the blower motor, and the outside fan in your air conditioner.

Checking Your Air Conditioning Capacitor

A voltmeter, if you have one, can tell you if you have blown a capacitor, but it’s even simpler to find out just by watching and listening. Take a walk outside to your condensing unit, and look and listen for the following:

  1. Do you hear any humming?
  2. Do you see the fan spinning?

If the A/C is humming but the fan is not running, you may have a capacitor problem.

A Simple Trick to Test if the Capacitor Is Working

If the A/C is humming but the fan is not turning, find yourself a long skinny stick. Gently slide the stick through the fan grate and give one of the fan blades a gentle push, to see if the fan will spin. If the fan takes off on its own and keeps going, you very likely have a bad start capacitor.

You see, the capacitor is there to give a boost to the fan motor upon startup. A capacitor stores power in a roll of electrically charged sheets of material.

When the capacitor is called to action, it is supposed to release its energy and give the fan a sort of electrical kick in the pants. If the capacitor is shot, the fan can't quite get going from just the 120 volts the motor supplies to it. You and your stick just took over the job of the start capacitor.

There are a few things that could have caused your capacitor to blow. The heat of summer plus motor heat could have proven to be too much for the part, or it could be something else.

Below I'll go over how to fix this problem yourself.

1. Start by Turning Off the Power

First of all make sure you know how to turn off power to your air conditioner. Don’t proceed if you do not.

  • Turn off the power to the unit at the disconnect or breaker panel, which should be mounted on the outside of the house within a few feet of the outdoor condensing unit.

It's always a good idea to double check that the power to the unit has been disconnected successfully with a circuit alert device. There's an example of a reliable and very inexpensive circuit alert device in section three of this article.

The disconnect box for the air conditioner.  The cover opens easily.

The disconnect box for the air conditioner. The cover opens easily.

On this particular disconnect, pulling the handle cuts the power and exposes the fuses.

On this particular disconnect, pulling the handle cuts the power and exposes the fuses.

2. Finding and Inspecting the Capacitor

After you have turned off the power at the disconnect:

  1. Remove the service panel on the A/C unit itself.
  2. Locate the start capacitor. (It's most likely silver, round or oval, and with multiple prongs on the top for wire connections.)
  3. Look at the capacitor surface where the prongs are attached, and ask yourself: does this surface look raised or domed?

One tell-tale sign that a capacitor is shot is its shape. When a capacitor blows, at least 95% of the time its top will be pushed up or swollen, somewhat resembling a pop can that has been dropped and is ready to explode when given the chance. Is this what you see? If so, this is good news, and we'll have you back up and running in no time.

It may not be pretty, but there's my capacitor.

It may not be pretty, but there's my capacitor.

3. Discharging the Power in the Capacitor

You've already shut off power to the air conditioner, but now you will have to discharge the power in the capacitor.

WARNING: As I mentioned, a capacitor stores power. That has not changed because you've shut off the flow of electric current. The capacitor may still have power ready to fire. Touching two of the terminals at the same time with your hand will discharge this power and make for a shocking experience. Throwing away a capacitor that hasn't been discharged could cause a fire in your trash can. Before you continue, discharge your capacitor by placing an insulated-handle screwdriver across the terminals, as shown in the video below.

Video: Discharging a Capacitor

4. Dismounting the Old Capacitor

Now that your old capacitor has been discharged, and you've re-confirmed that no electrical current is in the area where you'll be working with your circuit alert device (above), you can remove it. This is very simple. The capacitor is likely mounted to the unit by a metal band that has only one screw to remove. Remove that screw and the capacitor should come loose from the unit itself.

One screw and it's out.

One screw and it's out.

5. Noting Down How the Wires Connect

Before you remove the wires from the old capacitor, be sure to make a diagram or label showing what wire goes where.

Different colored wires go to different terminals.  This capacitor is good, so the top is flat, but if it were broken the area around the terminals would likely be raised like a shaken pop can.

Different colored wires go to different terminals. This capacitor is good, so the top is flat, but if it were broken the area around the terminals would likely be raised like a shaken pop can.

You can draw a picture showing where the different colored wires will connect to your replacement capacitor.

You can draw a picture showing where the different colored wires will connect to your replacement capacitor.

6. Disconnecting the Old Capacitor

Once you're sure where the wires will connect to the new capacitor, you can remove the wires using a simple pair of needle-nosed pliers. If the wires are tight, try not to just yank on them; use a rocking motion while pulling slowly. This will help keep you from touching another terminal, or possibly having the pliers slip and hit you in the face. Don't laugh, I've watched it happen.

That's it. Now all you need to do is obtain the right replacement part and re-install it just as you removed this one.

7. Choosing a Replacement

There are a couple of things you'll want to know when shopping for your new capacitor: the micro-farads (μF) and the voltage rating. The shape and size of the capacitor aren't really important as they can vary and still do the job. Even your mounting bracket will probably bend to accommodate a part of a different shape. Just know that you have to match the micro-farad number exactly. The voltage rating does not have to be identical, as it shows the amount of voltage the capacitor can see, not what it has to see; this means that if you need to you can use a capacitor with a slightly higher voltage rating than what you have now.

Your μF and voltage will be marked on your capacitor and will likely read something similar to 35/5 μF and 370V. If they are not written down, write down the make and model of your air conditioning unit, and use that information at the store or online to find the correct replacement part.

Lastly, brand is not important here. A capacitor is a pretty universal part, and should be available at your local contractor supply company, though maybe not at a Home Depot or Lowe's.

A capacitor for a residential-sized unit should be relatively cheap, and you may consider buying a second one for backup while you are there, along with a couple of spare time-delay fuses (but be sure to buy the right size fuse).

A/C Fuses

In the heat of the summer, blown capacitors and fuses are a very common cause of air conditioner breakdowns. If you suspect fuses are the problem, it can be an even easier fix. Take a look at the article I wrote about how to replace air conditioning fuses.

Your air conditioners fuses are located in the A/C disconnect that should be mounted to the house within a few feet of the condensing unit outside. Be sure if you are purchasing new fuses that they are of the proper amperage rating. You can always use a lower amperage fuse but never bigger.

If lower, the worst thing that will happen is they will blow again. If higher, they can allow a larger power spike to enter the unit and the result will be nothing less than a catastrophic failure in the unit. You are likely in need of two 20 or 30 amp time delay fuses.

Air Conditioning Maintenance Tips

I hope this was the answer to your A/C problem and that you were able to obtain and replace the part without any hang up for your family get-together.

The heat of the summer sun, added to the heat hard-working motors normally generate, can be tough on our air conditioners because hot electrical components break down more easily. So it's not surprising a part may fail on a hot day when you need it the most.

Keeping up on your A/C maintenance can help prevent these types of breakdowns. Keeping your air conditioner's coils clean and your air filter cleaned or changed when needed can keep the running temperature of your unit down, thus helping to keep your own temperature down when the summer comes calling.

For those with window units, when winter time comes around, you might want to remove the unit and store it somewhere to protect it from frost, dirt, and debris.

Thanks for stopping by, and again, I hope this helped you and saved you money.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: My outside AC unit starts running then stops. I hear a buzzing noise, then I hear no sound coming from the unit. What could that be?

Answer: It sounds as if something is tripping on an overload or there is bad contact in the circuit. I couldn't offer more without testing the circuit.

Question: I replaced the capacitors so the outside fan of my air conditioner would operate properly, but it is still not working. Is there anything else that I could check or try?

Answer: First, confirm that you have power and see if the breaker is tripped, or if fuses are blown. Check to see if the contractor is pulling in. The motor could just be bad.

Question: My air conditioner fan is running, but hardly any air is coming out of the vents. Could the problem be with the capacitor?

Answer: No, a capacitor does not affect air flow.

Question: Our AC fan turns on, but there is no cold air or hum. We had recently switched thermostats but have double checked all the wiring. It is in the 90’s and we can’t figure out what to try next. Would this be a capacitor problem if the fan is running? We are hoping it’s not the compressor. Everything was running great when it was shut down last fall.

Answer: You may want to make sure you don’t have two capacitors. Some units do. One for compressor and one for fan. Also, check to see if any frost or ice on the unit inside or outside, or on the lines that connect the two.

Question: My inside ac unit blower motor went out ... can that make my outside unit stop running as well?

Answer: If the blower in the air handler doesn't work then the coil will likely freeze if the outdoor unit does run so though the motor won't directly stop the outside, I highly recommend you don't try and run anything.

Question: My air conditioner takes more amperage and not cooling properly. What does this mean?

Answer: If the amperage is high, then something may be working too hard or about to go bad. That would either be the fan or the compressor.

Question: I have an older carrier unit that is not cooling. I replaced the capacitor, and it worked for about a week, but it's doing the same thing now. Do you have any idea of what could be the trouble?

Answer: Have you checked the amp draw on the unit? An older unit with parts working harder and harder with age could draw too much amperage. Are you sure you have the proper capacitor? Maybe double check what it came with from the factory to be sure. Extreme weather conditions can make this happen too, but so close together makes me believe you have a high amp issue causing it to overload and blow. These are just guesses since I can't be there to run tests of course.

Question: The company that installed my A/C about four years ago and service is it yearly said that I should put in a new competitor before the old one goes out. They say it would make my air conditioner work more efficiently. They want to do it for $199. Is it worth it?

Answer: That’s fairly reasonable but as I mention in the article, the capacitor is no more than $20-30, and if you’re comfortable doing it yourself then that’s what I’d do, but if you aren’t confident in working with electrical then it is worth it to have them do it.

Question: My fan only works when the RV unit is on. I tried to turn my unit off and leave my fan on, but the fan will not run without the unit being on. What’s causing this?

Answer: Check to be sure the green wire is connected to the “g” terminal on both the stat and the furnace. If it is, then you may have trouble at the stat.

Question: I replaced my capacitor, but the fan still does not spin even if I do it manually. All I hear is a click from the unit when I turn it on. Thoughts?

Answer: If that’s all you’re getting it sounds like a power problem. Perhaps a tripped breaker, blown fuse in the disconnect, or maybe a bad contactor. That’s what I’d be looking at. I have written articles on these issues that might help make that determination.

Question: I used the stick trick to fix my A/C. The fan started, and is still running. However, there is still no cold air. Is that to be expected until I replace the capacitor, or if it was indeed that problem, should starting the fan via the stick create the cold air?

Answer: The stick trick is just a way to help confirm the capacitor is bad. It does not make the unit work so yes, you’ll need to replace the capacitor for full function.

Question: I had to turn off all the power to our house. When I turned the power back on the AC unit would not run (had no power at all). Could this be due to power surge? If so, would this possibly be the relay or capacitor? If not, any suggestions?

Answer: It could be, yes. If it is hopefully it's just the fuses. I'd check those first. You would have power to the disconnect but not from if that is the issue.

Question: My fan blows inside, and the fan blades spin outside, but the air in the house is hot. Last night, I heard three loud popping noises outside before the AC started acting up. I then woke up to 82 degrees in the house. Could it be the capacitor or a more serious problem?

Answer: Yes and yes. It could be a capacitor, or it could be the compressor. Since capacitors are cheap it may be worth a try to see for yourself if that’s it, if not you will need a technician. There is really no “DIY” fix when it comes to repairing or replacing a capacitor.

Question: Our A/C thermostat was set to 72. However, the house will not cool below 77. I feel air blowing but I do not think the warm air is being circulate out of the house. Our filters are all clean. What could be the problem?

Answer: Your indoor fan can still run even if the outdoor unit is not. So you may want to see if your outdoor unit is functioning.

Question: My A/C unit doesn't come on from the thermostat, but I can manually kick it on outside, and it runs perfectly. Is that my thermostat?

Answer: If you’re kicking it on with a stick on the fan blade, then your capacitor is more likely the issue. If you’re pushing the contactor plunger, then it’s more likely your contractor. Does heat work? Will the indoor fan on option work? If yes, then the stat is less like likely the issue.

Question: My A/C unit's fan is blowing but the house is not cooling off. Is that a capacitor issue?

Answer: It could be if the compressor capacitor failed. Both it and the motor have them. Sometimes one capacitor does both and some units use independent capacitors.

Question: After a loud lightning strike with a surge in lights, our outside AC unit started humming loudly. Any ideas as to the cause?

Answer: Surges can take out everything or just one thing or nothing. I’m sorry but this would require someone to run significant tests to see what if anything is damaged.

Question: I replaced our capacitor a few months ago with a direct replacement and everything worked fine until today. I heard it buzzing again and looked to see that the fan was not spinning. I turned it off and on a few times during the day at the t-stat or the disconnect. It would start up for a little while before turning off again. I looked at the capacitor, and it still looks fine, but it did not meter. I can hear a faint buzzing when disconnect is pulled. Could it be a faulty capacitor, or is it something else?

Answer: The buzzing you here is your contactor. Maybe try to push it in (you'll see the button on the top of the contactor) with a stick next time it breaks down. If it's making poor contact, then that would explain why it's intermittent. Beyond that, I cannot say for sure what the issue is without coming out.

Question: So I just replaced the capacitor on my A/C unit outside. Once the unit gets to the desired inside temperature, it doesn’t kick off. Why is this?

Answer: There are a lot of possibilities that would require you running some electrical tests. Check the Stat and for a Short in the low voltage.

Question: Why does my A/C fan turn in the opposite direction?

Answer: If your fan is running backwards you have reversed the polarity. The motor likely has a way to reverse it back and is probably labeled on the motor itself.

Question: I replaced the capacitor of my A/C, but then when I plugged the disconnect back in it sparked, and now there is no power. What could be the issue?

Answer: It sounds like you blew the fuses in your disconnect assuming that’s where the spark was. You can replace those easily and cheaply.

Question: Our A/C stopped turning last night. The unit is working, but the fan won't turn, we replaced the compactor today, and it worked for 30 minutes before the fan stopped turning. I can spin it but it doesn't keep spinning. Could it be the contactor?

Answer: That is possible, but it would affect the whole unit, not just the fan.

Question: My Trane technician installed a new start capacitor. When he turned on the unit, it blew out the compressor. They are willing to replace it free of charge. My machine is 15 years old, but it was running well. Should I buy a new unit?

Answer: If they are willing to deduct the cost of replacing the compressor from the cost of replacing it and your budget allows it, then I would say yes. I would take advantage of that opportunity because your unit is likely an R22 system and the indoor section would have to be replaced too.

Question: My outside fan tries to start up but goes off in a second. I replaced the dual capacitor, fan and compressor, and it worked fine for one night. Now it starts for second and goes off again. The capacitor is tested and fine. What could be the problem?

Answer: You would need to verify all low voltage circuits are correct and sending proper "calls" and nothing is shorting creating false calls. Also, if the unit isn't satisfying the thermostat before shut down, it could be that the contactor is going bad or contacts are dirty/burnt.

Question: I have an LG window unit. It blows cold air, but I noticed today that when the set temp is reached instead of shutting off, the fan keeps blowing hot air for about 5 minutes and finally shuts off like its supposed to. Even when I manually turn the power off, the fan keeps running. Do you have ideas?

Answer: Window units aren’t typically worth repairing. It seems that your compressor may be running hot and if I’m not mistaken the fan will run until it cools down to a certain temp. It may be taking longer to do so due to high heat in the unit or perhaps the fan isn’t running as strong, or maybe airflow isn’t as good as it once was due to dirty coils. I really can’t say for sure because I’ve never spent any time repairing or troubleshooting these. Most people just buy new ones since the costs are so close most of the time.

Question: I just had my A/C unit go out and hired a repairman. He determined that it was the capacitor (45 7.5) and did not have the exact replacement part, so he installed two capacitors one 45 for the compressor and one 7.5 for the fan motor. My question is, is this ok to do (do they work together to ensure the compressor does not go on if the fan fails), and is there a risk that the fan capacitor may go and cause the compressor to break down?

Answer: No. What he did here isn’t an issue. I personally would rather have one for the sake of maintenance and space. I would be happy to do this to get a unit running but would probably buy a couple of the original one and put one in and keep the other as a spare due to how cheap they are and commonly the reason for a A/C failure.

Question: My air conditioning unit kicks on and the fan won’t run. I pushed it with a stick and the fan turns, but won’t stay on. What is wrong?

Answer: It is possible the fan is just bad. If you know you have power, the rest of the unit is running, and you've tried the suggestions in this article then it may be time to have the motor replaced. You should call a technician at this point however because there is very little more you can do yourself.

Question: As soon as the capacitor of my A/C was changed, the fan stopped blowing. Does that indicate fuse blown?

Answer: Not necessarily. If the fan was working why did you replace the capacitor? If the fuses are blown, you won't have power to anything.

Question: My A/C runs well, but after awhile the switch on the electrical box trips. Repair guy added 3lbs of freon and oil in the motor. The motor fan will stop, but when he hits it, it will start back up again. Do you have any suggestions?

Answer: While I can't say for sure what your issue is, it sounds like it could be the capacitor or a loose connection. I'm not sure what adding refrigerant (3 lbs is a LOT) did for tripping the breaker, and beating on the unit certainly isn't a repair technique. You may want to obtain a second opinion.

Question: My outside fan, won't start on its own. If I use a stick, it will start but seems weak and varies in speed. I suspect the fan motor. Also, the compressor will get warm/hot but doesn't cool at all. Does the capacitor impact operation beyond start-up?

Answer: Yes, it can and again, the stick is not a fix. It just helps confirm that the capacitor is the likely issue.

Question: My HVAC technician removed the capacitor and somehow made the connection "direct." Is my air conditioner safe to use?

Answer: I don’t think that’s possible. Are you sure he didn’t take out the contactor? If he did, that’s bad, and you need to shut it off at the breaker or disconnect, or it will run continuously.

Question: The problem I was having is the power feed wires, or whip, from the outside breaker was loose inside the AC unit. I fixed that by installing a new whip, or AC weatherproof wires. The problem I see now is that the fan does not seem to be running at full speed. Would the capacitor cause this problem?

Answer: Yes, the cap could do that and is cheap, so it's worth a try before considering a motor change.

Question: My daughter's unit started blowing warm air and it was freezing up outside. Also, the fan sounded louder than usual. The A/C guy came the next day. I'm not sure what he did, but it's been running nonstop ever since. Also, he said not to adjust the temp, to leave it at 72*. He didn't show up two days ago when he said he would and said he's supposed to come back tomorrow. Is this ok or even normal? He said he had to bypass something to make it run nonstop. Is this right or safe?

Answer: No. It's not right. I assume he bypassed the contactor and now when you cool low enough the thermostat will shut the indoor fan off and it will freeze up. Meanwhile the outdoor will keep running. All bad. Shut it off at the breaker or pull the disconnect outside. You can manually control the off and on at the breaker for now but make sure when the thermostat is satisfied you shut it back off and wait until the stat drops below the set temperature before turning back on. Not sure why the unit was freezing up before he got there, but it surely will now. Freezing up can be caused by low/no airflow, dirty filter, low refrigerant charge or pressure imbalance caused by a restriction in the lines. You should call a different tech.

Question: During my home inspection, I had an AC guy come and replace the capacitor in my central air unit; the unit started up fine. He then took the capacitor back out and was going to come back after I closed. I ended up replacing the capacitor myself, but now nothing happens. No humming, no fan, no nothing. Do you know what's wrong?

Answer: It's possible he pulled the disconnect or flipped it over (one side up connects the other, not the other way around) to prevent power from going to disconnected wires. It's fairly common practice to disconnect a inoperable unit. Or, you got the wiring wrong.

Question: After my A/C froze up, I was told to change the thermostat. After that was done the unit was put back on and there was a humming noise from inside the house but no air was blowing out of the vents, yet the unit outside was up and running. What may be my problem?

Answer: If your outdoor unit motor locked up (froze) and you have indoor motor issues, I'm inclined to say you had some sort of power surge because the 2 units are on separate circuits so nothing the outdoor did would cause the indoor to have an issue electrically. If you mean "froze" as in ice then the indoor motor probably wasn't blowing to begin with and is why it iced up. The ac requires air flow over/through the evaporator coil or it will freeze up and so can/will the copper lines between the two units.

Question: I will diagnose the starter capacitor later today, but I suspect that my compressor is the issue. Does this capacitor help start the compressor as well as the fan? If I find that it is the compressor is that something I can change myself (I’m assuming if I do it will require being recharged with coolant. Will a supply store sell it to me?)

Answer: Yes, the capacitor helps the compressor too, and no, I don't think the compressor is something you can do yourself. It requires a lot of expensive specialty equipment and a certification from the EPA. I highly recommend you call a technician if you need a compressor.

Question: My window unit makes a humming sound and ends up turning off all the power in the room. What does this mean?

Answer: It sounds like it’s shot and locked up this drawing too many amps and knocking out everything on the circuit.

Question: Is there a capacitor on the central air fan inside the house, as well as on the compressor outside of the house?

Answer: Yes. The blower motor in your furnace or air handler also uses a capacitor. Typically, it is a low MFD rated run capacitor, and not a dual capacitor.

Question: My indoor system sounds like it's running and is blowing air, but the outside system is buzzing, and warm to the touch. What would that be?

Answer: Did you check the capacitor? It sounds like what is being explained here in the article.

Question: No part of my A/C unit is working. There’s no buzzing, no fan spinning, just nothing. It has been out for two days, and the handyman that was called out claims that nothing is wrong. How do I fix this?

Answer: I'd start by checking all your power sources to make sure that you have power to the units, and that the stat is working and wired properly.

Question: My capacitor was replaced three years ago on this same date. Isn't $350 every three years a bit much for a replacement? Is there anything I can do to prolong its life, and should I get a cheaper source or repair company?

Answer: Well, capacitors can go more frequently than other parts, and sometimes it's because there is an underlying issue, but it would likely show more than every three years if there were. All that aside, $350 is highway robbery in my book. If you read the article, you saw that these aren't that expensive and aren't much harder to change than a battery.

Question: The fan of my AC is working, but I hear a buzzing noise when the compressor should turn on, and then it doesn't. Is this a capacitor problem?

Answer: It could be, but I can't be 100% sure without testing it. That said, the hum is most likely the contactor being pulled in and asking the unit to turn on. It could also be that the motor or compressor is locked up and trying to run.

Question: Hi Dan! I'm having issues with the fan on the outdoor unit. Everything starts, and the fan and compressor run (set to heat since it's winter) the warm air blows out inside. After a time (less than a minute) the outdoor unit fan stops. The compressor and the indoor blower etc. keep running. Since there's no airflow, the unit starts to ice up outside, and the warm air flow inside the house diminishes significantly. I can't see why the fan cuts out like this. Do you have any ideas?

Answer: The fan outside will kick off because it’s used to cool the compressor when needed. If it’s cold out, then the Fan doesn’t need to run. I don’t know why the outdoor unit is freezing up except that heat pumps don’t work well below certain temps and will shut off if it senses it’s too cold to run in which case your auxiliary heat should kick in.

Question: My AC was humming with no fan movement. I replaced the startup capacitor, and everything seemed fine. Now it's doing the same thing. The leads for the compressor move my multimeter set to 2k ohms and alternating lead contacts. I get nothing from common and fan leads, though. The fan doesn't start even if I use a stick. I'm thinking something else is causing damage to the capacitor. Any ideas what it could be?

Answer: Improper voltage from the disconnect/breaker, high temperatures, and bad motors/compressors are all suspects in repeated capacitor failure. A motor/compressor don't necessarily need to be locked up, but perhaps it is just slow to start due to bad bearings/pistons that are "grinding" just enough to drive up amperage.

Question: My compressor is running, but my fan will not turn on. Turning with a screw-driver is hard. What do you think is going on?

Answer: I can't be sure, but with how cheap most AC motors are, I don't think I'd try and repair one if it's even a repairable motor. It's pretty easy to change out as well.

Question: My outside A/C runs for about 10 to 15 minutes, and then blows the breaker in the breaker box in the house. Why is this?

Answer: Something is either shorted or working too hard (dying) and increasing the amp draw. You should call a tech to run electrical tests and see which component it is.

Question: My furnace unit runs fine but shuts off when the temperature is reached. There is a humming sound after it stops. This sound does not go away until I pull breaker?

Answer: It's most likely your transformer. It doesn't mean it's bad but some are just louder or more noticeable because of location of the unit than others.

Question: My AC is blowing a little cold air through the vents. The unit fan turns on, but after a while, it shuts off and then goes back on. What could be the problem?

Answer: Check your filter and have the coil inspected for build up or a good cleaning. An issue like this will likely need someone onsite to diagnose.

Question: I replaced the capacitors two days ago, the compressor and the fan starts up well but after a few minutes the fan stops running and only the compressor runs, I switched it off at once, after a few minutes if you switch it on again it does the same, what seems to be the problem?

Answer: I'm assuming you have a heat pump and the fan may not need to run. A fan cools the compressor for a/c. Not necessary to cool when in heat mode.

Question: I followed the steps, however, the hum was not coming from the capacitor. It is another component of the cooling pipes, what is that?

Answer: I'm a little unsure of what you mean by "cooling pipes," but if you mean the copper lines then there shouldn't be any component. They are just pipes. They could be vibrating, but it is rare. There's fluid and gas in them that you could be hearing travel. If the compressor is locked up, it could hum like a seized motor. Lastly, the contractor could be "chattering" meaning it's not making a good connection. However, pinpointing a noise is hard to do from here.

© 2012 Dan Reed

Comments

David Cheatwood on April 22, 2020:

Love this site. My a/c stopped working. It's only a few years old. Carrier heat pump. Thermostat clicks when cool or heat is set but not noise or action outside. I have 240 volts in the outside panel coming in. I checked capacitor. One side was fine but other side dead. Replaced with new same size. Still nothing. No ice anywhere. Filter clean and maintained.

Any thoughts? Where do I go from here? Thanks.

Aakash on April 11, 2020:

Hi Dan, I have window AC, when I turn on power supply to the AC, it's compressor gets start even I don't turn my AC on using PCB or remote, after turning AC on by remote/PCB then fan moter start as usual, but compressor keep running even I set the temperature to 16 to 30 degree celsius.

Zac on January 24, 2020:

Dan,

Hi. First, thank you so much for this very informative article and especially for all your responses to your readers' questions. It's beein a while since you've posted a reply, but if you're still there I've got one for you I didn't find in your list.

Our air mover wasn't working and I heard a hum from the unit when the thermostat called for heat. I tried the stick test and the fan started spinning, so it seemed like the capacitor. I disconnected to find the model/type and when I reconnected, the fan worked on it's own again with no stick (!). The next morning, the inside temp was below 60 and we were back to the humming and no fan.

I didn't test the capacitor itself, but found one at the local supply store and replaced it. The heat worked fine for a day, but overnight it seemed to stop and now it's back to humming with no fan spinning. Since the fan spins fine using a stick and the capacitor seemed to do the trick, I'm not sure what's going on. Any suggestions of what to check next?

Thanks!

talitha on September 26, 2019:

THANK YOU THANK YOU!! YOU SAVED US HUNDREDS OF DOLLARS (MAYBE MORE!)

Moesha Johnson on August 21, 2019:

How do I know what type of Dual Capacitor and Run or Start Capacitor to purchase? Where on my outdoor Air Conditioning unit must I look at to determine what brand it is? This way, I can assess respond to my own question I have mentioned above.

Big Al on August 14, 2019:

my central air gives off a vibrating noise about every 15 minutes otherwise AC works fine. any ideas?

Angela on August 10, 2019:

Plan an simple No air is coming out of my vents nothing is workjng the thermostat clicks and thats all i get. From my Ac Unit please help

Ryan on July 17, 2019:

My central air fan kicks but doesn’t keep running what might this be?

Samantha on July 17, 2019:

We have a Bryant Ac unit package and can’t find the capacitor and took off the entire front panel. Any idea where it might be?

Joe on July 16, 2019:

My A/C froze up last week and I thought it was because the capacitor was not turning on the fan. I also replaced the motor to be safe. It worked for a few days but now i hear a humming and the fan starting to run but stop.

diamond on July 14, 2019:

how do I detect AC compressor is damage

Andrew in Rockford MI on July 11, 2019:

Thanks for this helpful video. Sure enough capacitor was the problem. Your description and instructions were right now for my Bryant AC unit, can’t thank you enough.

Sherman on July 09, 2019:

My AC is not cooling the house properly during the heat of the day. What can the problem be , some freon maybe .Can I just get a technician to put a charge in it !

Tremblay Rejean on July 09, 2019:

You give me a lot of informations. Tank you very much...! 5 stars

Tamara Compton on July 08, 2019:

Our A/C unit is old.. A new capacitor was put on it and today it came on but was blowing out luke warm air. We let it run for a liitle bit until we couldnt stand the heat anymore.. We had to put our window unit back in. The a/c unit runs, blows out cool air, then starts blowing out hot air. We really dont have the money for a new unit.. Please Help!

Jan Ball on June 20, 2019:

I had an AC guy tell me I needed 2 parts in the condenser for around $500- I knew he was lying - but I needed my AC so I said OK- he pretended to put the parts in- then said I needed a whole new condenser --almost $6000- called a competitor - no new parts, found wire that had been deliberately disconnected!! $92 for service call!!

Rick on June 12, 2019:

I have a portable air conditioner LP. Fans are working fine. But no cold air is coming out of the air-conditioner. Can It be still a bad capacitor.

Perry hollis on June 05, 2019:

My outside unit starts and stops the outside fan runs so does compressor i installed new capacitor didnt help if i push the contactor in manually it starts and cools but when i remove the stick holding the contactor unit in shuts down the unit i was wondering if thermostat. Causing problems. Im going check the drain pan safety switch

Mike on May 30, 2019:

Outside Fan on comfortmaker a/c is laboring to start and runs noisily. The a/c will eventually shut off. Do I need to replace fan motor.

Brandon on May 19, 2019:

This was an amazing find! Thank you so much for this. Fixed my ac and made everyone in the family happy!

Curly on May 02, 2019:

I have a Lenox AC (4 yrs old) and it now has quit cooling. Thermostat turns on inside unit but never starts outside. I took the side cover off (outside) to look for relays and at the capacitor and there is test button with lights blinking say it is in standby. If I hit the test button it changes to yellow then red and the fan kicks on for minute and then shuts down. Coils look clean so I suspect freon low but also might be thermostat not sending signal? How could I test that it is signaling? Your thoughts and what a great service you offer to the "back-yard-mechanic".....Thanks.

nicole wallace on April 25, 2019:

Hello, I have a Bryant AC unit model # 698BNX036000ABAA and I saw the compressor capacitor is bulging and I want to replace it. The current capacitor is 45 uF, 370VAC, 50/60 Hz but I cannot find out online if this is the correct specs for the capacitor or if someone installed the wrong capacitor for this unit and that is why it has gone bad.

Ebi Sorbi on April 09, 2019:

My AC UNIT fan is working, cleaned up outside AC unit very well, changed the filter inside the house, My AC still blow hot air...

Does it still have to do with capacitor? or freon or compressor?

Thanks

Dan Reed (author) on September 19, 2018:

Christa, It sounds like the motor is going/gone bad but that would be hard to say for sure without being there to run electrical tests. Based on the given information that's about all I can offer. You may want to call a tech.

Christa on September 18, 2018:

My ac unit outside is only making a humming sound and the fan is not working when turned on. Last week it was making a horrible screeching sound while it was running and the fan would stop and go but now the fan won't work at all. Please help

Dan Reed (author) on September 17, 2018:

Amanda - Most of the time this is a result of a dirty filter (or other cause of low airflow) or a low refrigerant charge. The filter is easy for you to check but if it's clean then you'll likely need a technician to check for other issues.

Amanda on September 16, 2018:

My a/c keeps freezing up. Inside and out.

What could be causing that?

Dan Reed (author) on September 07, 2018:

Carley0219 - While I can't say that for certain, it certainly didn't help and was a bad idea if they left the unit on. I've done roofing and we did the same thing but we always pulled the disconnect and warned the homeowner that we had to shut down the unit temporarily. High heat is one of the most common causes of component failure so when the unit is covered and running, it can't disperse the heat it needs to.

carley0219@aol.com on September 07, 2018:

My daughters roofers covered her air conditioner on a 90 degree day and then it stopped working, and the air conditioner repair man had install a new capacitor. Do you think covering the unit caused the problem?

Dan Reed (author) on August 28, 2018:

Michael, It seems as if you've run out of refrigerant or the refrigerant isn't pumping. You're correct in noticing this being wrong but I can't be sure of the cause without being there and running tests however if it's all acting like it's working and this is your result, it usually means you're low on refrigerant. That would also mean there is a leak so I'd be sure the leak is repaired prior to spending a bunch of money on adding refrigerant...especially if it's R22. That is worth more than gold at this point so we don't want to waste it. That said, if you have a leak in an R22 system and the repair cost is substantial, I would strongly advise the consideration of a new system as opposed to throwing good money after bad.

Michael on August 28, 2018:

My central air unit turns on when switched on; however, instead of the unit fan blowing hot air outside, it feels cool, and the air coming out of the vents in the house isn't cold. Any thoughts on why it seems to be running in reverse?

Dan Reed (author) on August 20, 2018:

McClain - Your motor might be bad? Or the fuses perhaps? I really can't say without running some tests if this hasn't worked. You may need to call a technician.

McClain07 on August 19, 2018:

Hello.. My fan stopped running on the outside unite. I can hear the system running on the inside. I can also hear it try to come on the outside, but it doesnt. I reset the breaker.. Nothing. Air comes out the vents but its not cold. I tried the stick to move the fan but i dont hear a motor or anything.. Just only inside... Please help

Dan Reed (author) on August 17, 2018:

fbattle - I'm shocked that Carrier couldn't tell you this. With a model and serial number they should be able to tell you what screw holds the top on. There is no reason they couldn't tell you this. I would try again or find out who in your area is selling Carrier to the installers and they should be able to tell you. The motor may have it's capacitance marked on the rating plate but I'm not sure your compressor will.

fbattle on August 16, 2018:

When the capacitor went out last summer, the serviceman didn’t have the right capacitor on the truck, but said he could put a different capacitor on temporarily so we could have cool air and then would return later with the correct capacitor. He never returned as far as we know. I have not been able to find anybody, including Carrier technical support, who can tell me the specs for the original capacitor. Is there a way to find it from the model/size?

Dan Reed (author) on August 14, 2018:

Anthony - You may want to check out the contactor. I see your other question about pushing with a stick as well and if you're hearing clicking and the stick trick didn't help you diagnose, it may be the contactor is weak or fried and not allowing power to the unit. The clicking may be it attempting to connect but not quite getting it. Perhaps this will help you make that determination. https://dengarden.com/appliances/Air-Conditioning-...

Anthony on August 12, 2018:

Don’t know where clicking noise is coming from fan or compressor when ever I turn the ac unit on.

Dan Reed (author) on August 11, 2018:

The indoor blower also has a capacitor. Have you tried that?

Ulises on August 10, 2018:

Hey I have a problem with my ac I have a heat pump. The problem is when the ac stars the fan that go outside works but the fan that blows air to the house trough the air vents not working. But sometimes it works this is killing me. That means sometimes work and sometimes it work .. what could be the problem?? Help

Dan Reed (author) on August 06, 2018:

Theresa - I'm really not sure if you have an issue or not. All I can say is it's been a very hot summer where I am and so is mine. Perhaps the insulation, doors, windows, etc...are dated and the home is not holding temp as well as it once did. This is very common but again, you are not alone if you're having the kind of summer I am.

Dan Reed (author) on August 06, 2018:

Jane - I'm really not sure what a code 89 is but Honeywell does have a tech support hotline and website. customer.honeywell.com In the meanwhile you could bypass the stat and tie the red, yellow, and green wires together to make the a/c work if the stat is the only problem. Just REMEMBER TO UNTIE THEM TO TURN IT OFF. You can only do this for about 5-10 minutes at a time with breaks in between. Maybe keep a separate temperature gauge near so you know what the temp is. This makes you the thermostat and if you forget to do the thermostats job you could damage your whole system.

Dan Reed (author) on August 06, 2018:

Leyotuar - There would be a lot of possibilities. If you lost power then it's possible there was a surge when it kicked back on and that can sometimes take out more than one component or affect it's performance at least. You might want to have a tech check this out for you because there could be a situation where one part gets replaced and reveals another issue making it very hard for me to offer any sound advice.

Leyotuar on August 05, 2018:

Hi Dan-I went out of town and turned my unit up to 78. When I returned I have little to no air flow from my vents. My kids told me there were several pretty nasty t storms though the week. I have the same amount of air flow on cool and heat settings. When I turn unit off then back on all I hear is a click sound coming from the outside unit. I tried to spin fan blade and nothing.

Jane on August 04, 2018:

My AC honeywell thormsta has error code 89 . And we can't turn on the AC system. What is the problem?

Theresa on August 03, 2018:

My AC unit seems to run most of the time even when it reads the proper temperature on the thermostat it still seems to run I have changed The thermostat twice and both times it seems to do the same thing any helpers

Dan Reed (author) on August 02, 2018:

Kaelynn - While I can't say for sure what's happening you may want to consider the contactor as a suspect. If the contacts are charred or the coil in it is going bad perhaps it's not getting a good connection and causing it to be intermittent while the indoor unit is unaffected. DO NOT MESS WITH THIS if you are not confident in your electrical skills. https://dengarden.com/appliances/Air-Conditioning-...

Kaelynn W on August 02, 2018:

Our AC unit was working fine until our outside fan stopped working one day last week. My husband got it to go by starting it manually with a long screw driver. We thought we were good. A few days later it happened again. We replaced the capacitor. The fan now works intermittently...runs for a while and then randomly stops (I check when the air is not cold anymore). Then I turn it off and leave it off for a while. It usually starts back up. Could the new capacitor be bad? Could it be something else?

And we are not getting very good output of air from our vents. Is there something inside we need to replace? A different capacitor? We have cleaned the inside and outside coils. Nothing Ian freezing up with ice. And the outside unit was super hot when I turned all started.

Dan Reed (author) on July 27, 2018:

Mary Lou - You would need to know they put in the right capacitor and installed it properly. If so, then I can't see that being any cause of that. Perhaps a lightning strike? Any signs of that? A power surge can sometimes cause damage as well when power goes out and is restored.

Mary Lou on July 26, 2018:

I had a capacitor replaced on a Monday evening after my 6 year old AC unit with a 5 year warranty was not blowing any cold air. The AC worked until Saturday evening around 10:00P.M. when I heard a very loud sound and check the unit and the fan was still turning but was very loud. There also happened to be a bad storm going on at the same time. 2 hours later all the power to my house went out and I thought it was due to the storm. I called my utility company (on weekends you do not get a live person) and also tried to switch my house main electric several times,but no power. By Monday it was determined that the AC blew out the power and also that now the compressor was also bad , I was now informed I needed a new AC unit. My question is , the technician that came initially said the compressor was OK on Monday and by Saturday was bad, was the installation of the capacitor the possible cause of the compressor being blown on a 6 year old unit? And if so, how do I prove it to the company that did the repair?

Dan Reed (author) on July 23, 2018:

Maureen - That's really up to you but since they are only a few dollars perhaps you can keep one on hand in case it does go. Preventative maintenance is always good though. Better than needing after hours service.

Maureen on July 20, 2018:

Should I replace a capacitor on a blower that is still running, but at less than full power (tech says it was originally 7.5, now is at 6.72) or do I wait until it stops working completely?

Dan Reed (author) on July 19, 2018:

Sara - That is odd and I don't think it's the capacitor either. While I can't say for sure what is causing this I do know that some people with programmable thermostats will sometimes run into a schedule issue that perhaps was accidentally programmed into it and not realized. Maybe check to see if that is the case if you have a programmable stat.

Sara on July 18, 2018:

I’m in Texas where it’s record heat right now. My ac works fine (set at 76, stays at 76) until 2-4 pm until 11-1 am when it gets all the way up to 85! We have cleaned the coils, hosed it down, etc. someone suggested the capacitor, but it’s working fine in the am! Any ideas what to try

Dan Reed (author) on July 11, 2018:

It sounds like you're describing a window or thru the wall a/c unit. If that is the case, it sounds like the compressor is perhaps going bad and while that may not be what you want to hear, those units aren't typically worth the repair vs. replacing the unit. 13 years is pretty impressive though. That was a good unit.

Alexander Todea on July 11, 2018:

Hi Dan;

I am running a 13 year old GE in my bedroom, two weeks ago I noticed the compressor starting up only occasionally then no more, I changed the capacitor with a new one. After turning on the fuse and staring the unit, the compressor starts like a charm, when temp is reached it turns off and never on again. Switching off the main fuse and turning it on again after a few minutes and it will do the same thing again, compressor starts once only, no matter the settings...

Dan Reed (author) on July 10, 2018:

That could be the problem. If that capacitor blew you could still see all these things work.

Sean Holland on July 10, 2018:

A/C was cooling properly, however while the condenser fan turns on and the attic unit fan blows air through the ducts, it isn't cool air. Seems as though the compressor isn't running. There are two capacitors located at the outside condenser unit, I presume one for the fan and the larger one for the compressor? Suggestions appreciated

Dan Reed (author) on July 03, 2018:

Thank you Jeffrey! You too.

Dan Reed (author) on July 03, 2018:

Ricardo - I would. If the capacitance is low it is just a matter of time.

Jeffrey on July 02, 2018:

Thank you very much, Dan! I really appreciate your input, Keep cool, it's the hottest day of the year.

Ricardo on July 02, 2018:

An AC tech said my capacitor is rated at 80 but is only operating at 60 and should be replaced. What do you think?

Jeffrey on July 02, 2018:

Thank you very much, Dan! I really appreciate your input, Keep cool, it's the hottest day of the year.

Dan Reed (author) on July 01, 2018:

Jeffery - There isn't much any homeowner can do when the compressor fails. There are a lot of expensive tools and licensing required by the EPA to work on that type of repair. You're probably going to want to call a tech and be prepared. If the compressor is bad, the repair is expensive unless under warranty (in which case the labor still isn't cheap) and if your unit is R22 it's my opinion that repair is not a good idea and time to replace the unit.

Jeffrey on June 29, 2018:

Hi Dan, my AC quit working. The compressor outside probably stopped working for a few day untill I noticed yesterday because there is no cold air blowing from the venst inside the house. Unlike what you described here, the fan is running and from time to time, the compressor tries to start working (can hear the noise) and quit immediately. Any suggestion? Thanks a lot!

Dan Reed (author) on June 26, 2018:

It could cause issues since the rating is not in tolerance. These are not something you can just throw one in and expect it to work correctly. As stated in the article there is a tolerance. If you are not in that tolerance then it is likely you will experience problems. Is that your issue? I can't say for sure but should it be there? No.

Randall on June 25, 2018:

Would replacing a 40+5 capacitor with a 50+10 cause the condenser fan motor to shut off every 25 minutes while the compressor is still running.

Dan Reed (author) on June 25, 2018:

There could be a few different reasons it's doing this so I can't really say which cause and which effect. A/C's have hi temp limits, hi pressure limits, low pressure limits, etc...these are typically triggered when the unit's motor or compressor are working too hard as a result of low air flow, low refrigerant, age,...there are a lot of reasons. The problem is these are usually a replacement type part in themselves. You are usually going to have to address an underlying problem that is causing this (like having the a/c cleaned for better airflow to cool the unit) or the part itself is bad and would have to be replaced. (new motor or compressor) Sorry I can't identify it exactly.

stephanie gagnon on June 25, 2018:

my ac outside unit cuts off but i can turn off the a/c for 15 minutes and turn it back on and it works fine, what could that be

Dan Reed (author) on June 25, 2018:

You'd be supplying too much of a kick to the parts being fed from it. It may even work fine initially but eventually you'll have issues.

Randall on June 24, 2018:

What happens when you replace a 40+5 capacitor with a 50+10 on an outside split unit

Dan Reed (author) on June 21, 2018:

Samantha - Sorry but no I can't say what goes in there. I don't deal in that brand or type of equipment and it's a bit different of a ball game dealing with campers and RV's than homes.

Samantha on June 21, 2018:

Hi I'm staying in a camper with an air conditioner thats no longer working! The unit is a Coleman TSR and under the cover on the inside is a sticker that reads series 6750 air conditioner! Can you tell me what kind of capacitor it needs so I can tell my friend over the phone that way he can pick one up before he comes to fix it?

Dan Reed (author) on June 19, 2018:

Russell Wilson - High amp draws and extreme conditions can cause this to happen but beyond that I really can't say. Sometimes is cheap manufacturing and others there's an underlying issue driving up the electrical draw... The one you just bought should be under warranty however so perhaps you try once more and see if you just got a bad part right out of the box.

Russell Wilson on June 19, 2018:

Why does the capacitor go out? We replaced one Saturday, two days ago, and it worked like a champ for 3 days. It’s now doing the exact same thing. What should I address next? I appreciate your time and look forward to your response.

Dan Reed (author) on June 19, 2018:

Well it could but it wouldn't be anything you can reset yourself. Perhaps try shutting down the unit for a few minutes by shutting down the stat, then the breaker. Leave it sit for a few minutes then turn the breaker back on and then the stat and see if that might reset the switch. (if that is in fact the issue.)

Kristin on June 18, 2018:

I replaced my capacitor due to the fan not starting up and everything runs outside now, but the air isn’t cooling. I was told there may be a high pressure reset switch but I cant find it...the advice I’m being told is pointing to the compressor not engaging to cool air. Does this make sense?

Dan Reed (author) on June 17, 2018:

Check a few of the simpler things like the low voltage wiring. Green and yellow in particular control the a/c (off on - yellow) and fan on (green) check at the stat and the circuit board. Do you know how to test voltage? If so, check at the board that it’s sending power to the fan terminals. It could be a bad motor but it could be simple loose wire or bad board. That’s what I would check first.

Jerry on June 15, 2018:

Hello Dan,

First I want to say thanks for all info you providing and answering the questions.

My outside unit works fine. But inside fan doesn't blow the air in the house. Symptoms point on capacitor which I changed today and nothing. The problem is still here. What would you advise to check next?

Any input is highly appreciated.

The AC works itself."tube" is cold. Heat starts only on aux heat for some reason. I dont know if it's related.

Unplugged every cords and plagged it back in. Fan motor problem? Motor relay? Cup? How do I diagnose what is it?

Thank you

Dan Reed (author) on June 11, 2018:

You're welcome Robert. The capacitor itself should have the information you need written on it. If not, you can find out who the local Nordyne distributor is and give them your model and serial number and they should be able to tell you what's supposed to be in there so you can get the replacement.

Robert on June 10, 2018:

Very helpful. I attempted the fan blade test and it worked. Now just to locate the capcitor on my FS3BA-036KA..(not located on outside). Thank you Dan!

fazedbygrace on June 06, 2018:

thank you for your answer, I do understand all what you said, I did some checking and my pan is dry, the capacitor looks ok and both units (bonus room/teen bedroom and main level) fans are working fine, thermostat clicks on, all air is cold from vents (have had leaks in other homes) just not coming out of vents at any kind of force, so I am thinking maybe blower or relay to blower? And I will check my filter but it was just changed in March. thank you for you advice, it is upfront and honest, I appreciate the tips too!!!

Dan Reed (author) on June 06, 2018:

fazedbygrace - First, I always recommend making sure the filters are clean. I'm not sure if you're describing that there are 2 systems in the house (one for attic and one for main living) so if there is, it's possible the attic unit ran while the living area did not and thus the difference. Beyond that, leaving the temp up at 82 while you were gone probably allowed a lot of humidity to sink into the home, woodwork, carpets, etc...so it can take a couple/few days for the a/c to first remove the humidity (because that's really what an a/c does) and then once that occurs the temp will begin to drop much faster so perhaps just a little more time is needed. If not, then I would have a tech come and look for a problem. Always be leery when a tech says they need to "top off the refrigerant". That is not something that should ever be necessary unless there is a leak in the system and if there is, it should be repaired or sealed prior to any more refrigerant being added. That is one of the most common "suspicious" diagnosis that I hear people getting. Aside from that, I really can't offer much sound advice without being there. I've written many articles on HVAC however so perhaps reading a few of them can give you a better idea of how systems work, what parts do, and either how to fix them or at least understand better what a tech is saying when he comes out and starts telling you what's wrong. I hope this helps a bit and thank you for reading.

fazedbygrace on June 05, 2018:

Hello, I found this page by searching for information. I am an older woman with no husband who is determined to not be taken to the cleaners by repairmen thinking I am clueless. 9Has happened over the years many times). So I come home from vacation last night. there were many many storms in our area while I was gone. Power outages occurred. But my homes time keepers were NOT blinking, so I have no idea if my power actually went off. I had set myAC to 82 degrees while gone, and lowered the temp upon return last night. I went to bed, did not notice extra heat, or anything at all other than teenager has bonus room and attic is accessed in that room and he left light on while gone, so I went up to turn it off (and to make sure no one was in my attic), I noticed immediately that it was cooler inside the attic in GA heat than in house and I know that is an unusual occurrence, normally that rooms AC runs continuously depsite temp inside room because the thermostat is on the attic wall and is always hot (separate unit for bonus room). Today did not notice it hot in house, but warm, came back home and felt it was warmer, checked AC, temp setting was on 68 and room temp showed 78. That never happens. Motor is running outside. Not sure of fan, its currenlty 1254 AM amd I am not that brave (coyotes are here), in attic furnace/unit is running but sounds like no air being pushed through vents and vents have cool air but very very little flow. My cousin has always serviced my AC and furnace but he moved to Tampa to his AC business there. When I turn fan only on, no big change in air flow. Im worried abt coils but area is absolutley bone dry (I was concerned abt this as this unit was replaced for this very thing as it had fallen in on previous owners, but all is fine.), So from this information what do you think I could check or just be aware of/suspicious of whats up with my AC if I have to get a service pro out? Thank you in advance for any advice you can give. Iam capable of changing a capacitor via instructions, just unsure about where to start checking currently for options to repair on my own!!!

Dan Reed (author) on June 05, 2018:

John B - It could be but that doesn't mean it is. Often, breakdowns will happen after having sat for a season and then the first time it kicks on...whatever was about to happen does. Perhaps a capacitor, fuses, tripped breaker, contactor is dirty...there are a plethora of possible things that could be happening. Unfortunately, just not enough information for me to say much more than that with confidence.

John B on June 04, 2018:

I turn on my A/C the other day and my furnace blower came on but no noise from outside ? No hum, No fan ? Worked fantastic last year.. Could this be just my capacitor ? Thanks

Dan Reed (author) on June 04, 2018:

Siraj - I don't believe your capacitor has anything to do with your issue in this case and I'm not sure there is anything you can do to shorten that restart time. Perhaps unplug the unit for about 30 seconds and then plug it back in and see if that might help.

Siraj on June 03, 2018:

Hello every one

I have window ac.. as there is low voltage problem in our area and when there is glitch in voltage my ac compressor just turn off and it almost takes 7 to 9 minutes to start again... is there any problem with the capacitor? I just want to reduce the restarting time of my compressor to 2 or 3 minutes..thanks

Dan Reed (author) on June 03, 2018:

Snyteacher - Did they say why they added refrigerant? That shouldn't be necessary unless there is a leak or was never right. There is never a need to add refrigerant without one of those reasons. $100 isn't bad for what was done considering a service call alone is around $80 where I am. i don't think a capacitor is the issue. Maybe there's a short or perhaps your panel is overloading?? There's a pull for too many amps coming from somewhere.

snyteacher on June 01, 2018:

The fan stops because the breaker keeps tripping at the main panel. The fuses are fine. I had a repairman out here about 1 week ago and they checked everything. I paid $100 for them to turn the breaker back on, add refrigerant and clean the coils and check the fuses. Could it be the capacitor?

Dan Reed (author) on May 30, 2018:

sls535 - Well testing for capacitance is the fool proof way but most people don't posses a meter or knowledge for doing so. That said, if the unit is running then the capacitor is not likely the issue. The outdoor unit is supposed to blow warm air if that is what you're referring to. If everything is running seemingly proper and you're still getting warmer air, you may have a refrigerant charge issue but that would require a tech and specialty tools and licensing to test and determine.

sls535 on May 29, 2018:

Hi Dan,

Thanks for your knowledge and generosity.

My Lennox dual zone AC unit is blowing warm air. I've checked the capacitor and (unfortunately), I'm not seeing the soda can bubble.

I know you mentioned that this is a 95% probable sign, but can you provide guidance on determining 100% capacitor reliability?

thanks again!

Dan Reed (author) on May 29, 2018:

Christy Trotter - I'm sorry but there isn't much advice I can offer on this one without running some tests however I can say I do not think it's the stat because whatever it would be telling the outside unit would affect both parts, not just the compressor.

Christy Trotter on May 29, 2018:

I have a Lennox outside air unit. Ive noticed that my unit kicks on and u can see the fan working. Then the compressor will finally kick on a few seconds after that. Then everything is going fine then all at once the compressor kicks off and then rite back on. It does that a few times. Then finally it will cut off like it should. What could be causing this problem? I was thinking it could be the thermostat.When the compressor is kicking on and off the fan keeps going.

Dan Reed (author) on May 25, 2018:

katostein - I'm not sure what it was doing in the first place so it would be hard for me to say what should be different. If replacing the capacitor didn't work then you may have a different issue. Keep in mind the skinny line shouldn't be cool at all. It should be warm. The larger one should be cool or even sweating under certain conditions. If these are not the case then you may have a refrigerant pressure issue and that is not something you can try and remedy yourself.

katostein on May 24, 2018:

hello i have an older Carrier unit, just replaced the capacitor and a week later it is acting the same way. the outside line is barely cool to touch.

any ideas??

thanks!!

Dan Reed (author) on May 22, 2018:

Robin - Make sure you try to spin the fan both ways with the stick to ensure you're going in the right direction or it won't spin. Otherwise, you may have a bad fan motor, perhaps bad contact in the contactor (make sure the button/plunger is pulled in all the way...you can push it in with a stick too to see if that is making good contact.) Make sure your fuses aren't blown or the breaker is tripped so that you know you have power because the hum could just be the contactor pulling in that is getting power from the furnace, not the a/c power lines so you can have power from one and not the other. Hope this helps give you a few more things to check and see if you can get it working. Beyond that you'd really need to call a tech out to run tests. Thanks for reading.

Robin on May 21, 2018:

We noticed the fan in the outside A/C unit isn't turning, and there's a very audible hum coming from the unit, as if it's trying. The air is blowing inside, can't tell if it's cold, but when we give the fan a push with a stick, it doesn't keep turning. (It stops)

Any ideas??

Dan Reed (author) on May 14, 2018:

First, I'll guess capacitor but that's just a hunch. The issue is, why does it keep blowing. I'm assuming they aren't there all day when they fix it and they are just fixing the immediate issue but the fact that this keeps happening, they should be looking for the "why". You should be able to verify your warranty through whomever sells that brand of equipment in your area. Call and give them your serial number (maybe model too) and they should be able to tell you.

Mark on May 13, 2018:

Every year since I’ve bought the house ( 4yrs) my air goes out st the beginning of summer. It’s been under Warrenty but I don’t think it is anymore. I don’t know what they do when they come out. But it’s symptoms are: it hums and doesn’t start and then I hear a noise like a poof. And then there’s no noise. Any help would greatly be appreciated.

Dan Reed (author) on May 13, 2018:

There are capacitors in both. The one inside is for the fan in the air handler/furnace and the one outside is for the heat pump.