How to Remove a Mildew Smell From a Window Air Conditioner
Why Does My A/C Smell Bad?
Many homeowners take advantage of window air conditioners to save money on electric bills, cool down areas of their homes that the central air unit doesn’t reach, or make their room cold enough to be able to use a blanket at night.
A window air conditioner can be useful for all the reasons listed above, but when dust, water, and heat are combined, they provide the perfect environment for mold and mildew growth if no annual maintenance is performed.
Where Did That Mildew Smell Come From?
There are several possible reasons for that musty stink:
- Window air conditioners have a drip tray that is a necessary component of the system. This collection of water, along with heat and dust, allow for some pretty nasty “muck” to collect over time. The smell associated with this stuff is best described as being sour, moldy, or mildewy.
- If there's a drainage problem, water may have pooled and mildew may have grown on the filter, condenser coil, or somewhere else inside.
If the mold is black (Stachybotrys), it's toxic, and you'll want to get rid of it as quickly and thoroughly as possible. I've outlined some steps below that people take to remove the smell, but it’s always best to refer to any literature that came with the window air conditioner at the time of purchase.
WARNING: Most window units are pressurized systems and have a charged capacitor that could cause a shock, so at no time should a homeowner remove anything other than the case, which exposes the internal components of the window air unit. Doing anything other than removing the case may result in personal injury.
Seven Steps to Get Your AC Smelling Right
Step One: Remove the Case from the Unit
On smaller window air conditioners, remove the outer metal case of the unit. This should expose the coils, fan, and compressor. In a larger unit, after the front plastic and a few screws are removed, the air conditioner will slide out of the case toward the inside of the room. Be careful not to damage the metal fins on the front and rear of the unit. These are made from aluminum and will bend easily.
Step Two: Take It Outside
Choose a location outside where a hose can be used, such as a driveway. Place the window air conditioner on something secure such as a couple of saw horses or a secure table of some kind. The table or saw horses will be exposed to water and bleach, so choose something appropriate for this task. For larger air conditioners, an assistant may be required to lift the unit.
Step Three: Remove Dust
Blow the unit off with compressed air from a distance sufficient to remove dust and debris, but be careful not to damage any components or blow too hard on the aluminum fins. Wipe off any surface dust or debris with a damp cloth.
Step Four: Clean the Fins
Using a soft brush such as the type used to remove lint from a dryer vent, stroke the fins up and down to remove debris caked on to the front and rear of the air conditioning unit.
Step Five: Clean the Vent and Blower
- Fill a spray bottle approximately ¼ full of bleach and fill the rest with water.
- Spray directly into the area where the cool air blows out of the air conditioner. Saturate this area. Be sure to get plenty of the solution into the blower fan while turning it slowly.
- Once the bottle is empty, refill with water and spray in the same area.
The goal here is to clean the area with bleach and water, then flush the bleach out with water.
Step Six: Flush Tray With Water
Using a hose, flush all the muck and debris out of the drip tray. Do not spray in the tray. The goal here is to use enough water to flush out the debris, but not to use much pressure.
Pressurized water will damage the window air conditioner components. Flushing for several minutes is usually enough to sufficiently clean things up.
Step Seven: Let It Dry
Allow the unit to dry for a few hours. Inspect it closely for any damage or debris. Wipe up any remaining water with a dry cloth and wipe down any surfaces that still need cleaning.
Step Eight: Reassemble
Reassemble the case in the reverse order and slide unit back into the case that it was removed from.
This should be enough to remove the smell from the window air conditioner. These steps should be taken at the end of every warm season. The window unit should be stored in a clean, dry location over the cool fall and winter months.
Tools and Items Needed
Dryer Lint Brush
Saw Horses or Old Table