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How to Fix a Fridge That Isn't Cold Enough

Eugene is a trained engineer and self-taught home improvement enthusiast with almost 40 years of professional and DIY experience.

Original uncaptioned image, © Milad Mosapoor on Wikimedia Commons

Original uncaptioned image, © Milad Mosapoor on Wikimedia Commons

Unlike washing machines which have lots of moving parts that can go wrong and are subject to a lot of wear and tear, refrigerators don't normally give much trouble. In fact our first fridge lasted nearly thirty years! Sometimes however, the interior temperature can fail to drop sufficiently, potentially causing food to spoil. In this guide, we outline some troubleshooting tips you can try, before reaching for your wallet to buy a new one!

What's the Ideal Temperature for a Refrigerator?

The U.S. Food and Drug Administration (FDA) recommends keeping the inside temperature of a fridge at or below 40°F. Ideally it should be less than this. The table below shows what's recommended in different countries by government food safety agencies (See "References" at the end of this guide for links to articles)

AgencyTemperature

U.S. Food and Drug Administration (FDA)

40°F or less

Food Standards Agency (UK)

5°C or less

European Environment Agency (EU)

1 - 4°C

Food Safety Authority of Ireland

0 - 5°C

You Need A Thermometer to Measure Temperature

Yes, that's obvious, but which type?

  • Alcohol-in-glass. This type of thermometer uses a liquid enclosed in a tiny channel inside a glass encapsulation to indicate temperature. The liquid expands as temperature increases (and vice versa) and the position of the top of the liquid indicates temperature on an adjacent scale. Mercury-in-glass thermometers, such as lab thermometers, although they respond quicker and can be more accurate, are not recommended because mercury is very toxic and can contaminate your fridge and food if the thermometer breaks. You can use a room thermometer or buy a fridge/freezer thermometer which is likely to give more accurate results.
  • Spiral strip bimetallic thermometer. This consists of a strip of two metals wound into a spiral. As temperature increases, the spiral unwinds. A pointer attached to the spiral strip moves over a scale, indicating temperature.
  • Digital thermometer. Temperature is sensed by an electronic sensor and shown on an LED or LCD display. Digital thermometers can have the sensor enclosed inside the display unit, or attached via a separate cable (This is useful for testing the temperature inside a chest freezer while the lid is kept closed)
Alcohol-in-glass room thermometer.

Alcohol-in-glass room thermometer.

Things You Can Try If Your Fridge Isn't Cooling Down Enough

1. Check the Obvious First — Adjust the Temperature Control Knob

You mightn't even have noticed this especially if you're one of those people who don't read manuals! The temperature control knob isn't always obvious, especially if the fridge is an under counter model. Sometimes it's under the icebox, on the back wall of the appliance and you won't see it unless you get down on your knees. The control knob will have numerals (typically 1 to 5) or other marks for setting the temperature. The higher you set the number, the cooler the fridge will be. In hot weather, the thermostat doesn't regulate the temperature as well, so you have to manually turn up the knob to a higher setting to compensate. Try this if your thermometer reads too high and see if it works.

Temperature adjustment control.

Temperature adjustment control.

2. Defrost the Icebox

Layers of ice on the icebox prevent the cooling coils from absorbing heat from the food compartment. Fridges with auto defrost will defrost this ice automatically, alternatively remove food and store it in a suitably cool place (using cooler boxes, wrapping in insulation etc), pull out the plug of the fridge and allow ice to melt. This is a good time also to give a fridge a spring clean on the inside. Vinegar and baking soda are excellent for cleaning food residue.

3. Rearrange Items in the Fridge.

If a fridge is overpacked and items stuffed up against the icebox or against the cool back wall, it can prevent air circulation or absorption of heat by the cooling coils. Rearrange your food and drinks to stop this happening.

4. Check the Light Isn't Staying On

A switch on the side wall of a fridge shuts off the interior light when the door is closed. The lamp in a fridge is normally an incandescent type and can generate enough heat to rise the temperature in the cavity. Close the door and check the light goes off when the door is almost closed.

Light inside a fridge.

Light inside a fridge.

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5. Clean the Condenser Coils

Heat from the interior of a fridge is pumped out via narrow bore copper pipes to a condenser or heat exchanger at the back of the appliance. This works like a radiator in a home heating system. Air cools the heat exchanger and refrigerant inside and carries away the heat. The coils and fins of the condenser can become covered with cobwebs and dust, reducing their effectiveness at transferring heat to the surrounding air. You can clean the dust off with a soft brush and vacuum cleaner or use a brush accessory on the nozzle of the vacuum.

Condenser at the back of a refrigerator. Heat from inside the fridge is removed from the circulating refrigerant by ambient air.

Condenser at the back of a refrigerator. Heat from inside the fridge is removed from the circulating refrigerant by ambient air.

Clean the coils with a soft brush or brush accessory for a vacuum cleaner.

Clean the coils with a soft brush or brush accessory for a vacuum cleaner.

6. Make Sure the Room is Warm Enough

Some fridges/freezers need a minimum ambient room temperature for the refrigerant to work properly. If your fridge or freezer are in an unheated room or garage, the temperature may drop too low in winter, preventing the refrigerant from working. The ambient temperature should typically be more than 10°C (50°F), but this Black & Decker model recommends 55°F. The minimum room temperature depends on the refrigerant used in a fridge, so check the manual that came with your appliance or search for a manual online and download a copy.

7. Is the Room Too Warm?

Similarly if a room is too warm, the air surrounding the condenser coils may not be able to properly cool the refrigerant, preventing the interior of the fridge from cooling down sufficiently.

8. Provide Sufficient Clearance for Air Circulation

Air has to be able to circulate under, around and out the top of a fridge in order to cool the condenser coils. There should be a minimum gap between each side of the fridge and adjoining cabinets and also between the top of the fridge and the underside of the countertop. Typically the gaps should be 1" to 2" (2.5cm to 5cm). There should also be a gap between the condenser and the wall behind. Usually spacers are attached to the condenser, preventing the fridge from being pushed back too close to a wall.

How Much Does it Cost to Run a Fridge?

A small undercounter fridge will typically be rated at about 60W. However the average power rating will be less than this because a fridge has a varying duty cycle. This means that it isn't powered up constantly. Instead, it cycles on and off, controlled by a thermostat. The higher you set the temperature control, the greater the duty cycle and the longer the fridge stays on before switching off when the temperature inside reaches the setpoint. The duty cycle is the fraction of time an appliance is turned on. You can check the duty cycle and number of kWh used with a power monitoring adapter. See my guide "Checking Power Consumption of Appliances With an Energy Monitoring Adapter" for information about this.

Working out the cost of running a fridge

Simply divide the power rating by 1000 and multiply by the duty cycle, number of hours and cost per unit.

Example: A 60 W fridge has a duty cyle of 30%. If electricity costs 18c per unit, how much does it cost per day to run the fridge?

Cost = 60/1000 x 0.30 x 24 x 18 = 7.8c approx

Power and energy monitoring adapter. This version has a UK socket, but adapters with socket types for other countries are of course available.

Power and energy monitoring adapter. This version has a UK socket, but adapters with socket types for other countries are of course available.

How a Fridge Works

References

Commissioner, Office of the. (n.d.). Are you storing food safely? U.S. Food and Drug Administration. Retrieved August 2, 2022, from https://www.fda.gov/consumers/consumer-updates/are-you-storing-food-safely

Home cooking and storage. Domestic Practice | FAQ' s | The Food Safety Authority of Ireland. (n.d.). Retrieved August 2, 2022, from https://www.fsai.ie/faq/domestic.html

The recommended temperature for a refrigerator is between 1 – 4 °C. European Environment Agency. (2020, October 15). Retrieved August 2, 2022, from https://www.eea.europa.eu/archived/green-tips/the-recommended-temperature-for-a-refrigerator-is-between-1-2013-4-b0c

Chilling. Food Standards Agency. (2017, December 18). Retrieved August 2, 2022, from https://www.food.gov.uk/safety-hygiene/chilling

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Eugene Brennan

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