What Causes Refrigerators to Freeze Up?

Finding food in your refrigerator that has frozen can stress both your menu and your budget. You can often address the problem, however, with a simple repair or adjustment. Your refrigerator is constructed to circulate cold air from your freezer, cooling the contents of the refrigerator compartment below, beside or above it. Take action when frozen refrigerator contents tell you that air-circulation is out of control.

Morning juice
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Juice being taken from a refrigerator.

Thermostat

The thermostat measures temperature and regulates power to the compressor and the evaporator and compressor fan. Turning cooling controls off and on and listening for a power hum gives you a general idea of whether the thermostat is functioning. Placing an inexpensive appliance thermometer inside is the most accurate way to measure the exact temperature inside the refrigerator compartment. If settings vary or frequently dip to freezing, a broken thermostat is the most likely cause. Replace the thermostat.

Checking the Thermostat Setting

It is easy to change the thermostat setting inadvertently when loading or unloading the refrigerator. Since many cooling controls are labeled with numbers, like 1 through 5, or letters, you can change the temperature without knowing the exact degrees of change. To prevent bacterial growth and food poisoning, the refrigerator compartment should register between 36 and 39 degrees Fahrenheit. Above this narrow range, food can spoil; below it, food is in danger of freezing. Use your thermometer to check the correct level at which cooling controls should be set, and do a quick visual check when you load or unload the refrigerator.

Fan

Fans assist in moving cold air from the freezer into the refrigerator compartment. While a broken fan most often manifests as a warm compartment, overpacking the refrigerator can interfere with cold sensors, causing the fan to overwork. A constantly running fan can produce frozen food in the refrigerator. Rearrange food to determine whether you can re-stabilize the system. Since the path of cold blowing air travels down the back wall of the refrigerator compartment, putting food in the back on the bottom shelf can expose it to excess cold. The crisper drawers below the bottom shelf are designed to shield produce from this stream of frigid air.

Damper

Dampers also control the flow of chilled air from freezer to refrigerator. A jammed or broken damper can let too much air flow in, freezing food. Since the damper is usually at the top of the refrigerator compartment, it may be the culprit if food is freezing primarily on the top shelf. Damper valves function in coordination with fans but can develop problems unrelated to the fan.

Drain

Freezing can occur when cold water, which flows in a tube down the back side of the refrigerator, is blocked from reaching the bottom tray where it evaporates. A clogged drain can result in frozen puddles on the refrigerator floor or the back wall of the compartment. You can usually unjam a drain easily with a piece of wire, although take care not to puncture the plastic drain tube.

Thermistors and Electronic Issues

If you have not yet determined a cause for freezing, you may have a faulty thermistor. These electronic temperature sensors affect the functions of the fans and damper, and every refrigerator model may have several of these sensors, which can be damaged by water leaks or age. As part of the refrigerator's electronic system, thermistors may be most easily evaluated and replaced by a professional.