At one time, all refrigerators required manual defrosting when ice built up in the freezer, as this buildup prevents the unit from functioning properly. Today’s refrigerators are mostly frost-free, which means they defrost themselves to prevent frost buildup. Problems with the defrost timer can prevent this process from working the way it should, and cause other issues that keep a refrigerator from running efficiently. When it seems like the refrigerator or freezer just cannot keep up, before calling for appliance repair services, check the defrost timer. More often than not, a problem with this mechanism is the culprit, and it is easy to diagnose, even without arranging for freezer repair services.

Symptoms of a Defrost Problem

When a frost-free refrigerator has trouble cooling, or the freezer begins to build up frost, there may be a problem with the defrost mechanism. In order to determine this, the evaporator cover and coils at the back of the freezer must be checked. If the cover and coils, or even just the coils are covered in ice, a defrost problem exists, which may require the expertise of a tech from freezer repair services.

Mechanical Defrost Timers

Frost-free refrigerators automatically perform defrost cycles to keep frost from building up, preventing the need for manual defrosting. These defrost cycles are accomplished with a mechanical defrost timer or a digital, adaptive defrost sensor. Based on the way they are set, mechanical defrost timers run a defrost cycle every few hours to prevent frost buildup. It is reasonably easy to troubleshoot and replace defrost timers when they go bad, which often does not necessitate a call for appliance repair services. Defrost timers are usually found either under the front grill of the appliance, in the refrigerator next to the temperature controller, or on the back of the refrigerator.  

How Defrost Timers Work

Mechanical defrost timers work very simply. According to how often the timer is set to function, it shuts off the power to the cooling system, while running the defrost heater for a few minutes. This prevents the evaporator coils from freezing up. Once the heating part of the cycle has been completed, the timer turns off the defrost heater and resumes powering the cooling system.

Troubleshooting the Defrost Timer

Mechanical defrost timers are notorious for getting stuck, which means they either prevent the heat function from starting - allowing frost to build up, or they get stuck in the heating position - preventing cooling. When either of these things happen, either the timer itself, or the thermostat in the timer must be replaced.

A defrost timer can be tested by advancing it to the next cycle, then waiting to see if it works the way it should in turning on the defrost heater for a few minutes, then shutting it off again. If this does not occur, and the timer does not advance to the next cooling part of the cycle, there could be a problem with the timer thermostat. The defrost timer can be taken apart and the timer thermostat visually and electrically tested and replaced if necessary. When the defrost timer fails to advance at all, staying in whatever position it is advanced to, it is likely that the timer motor has burned out. In this case, the entire defrost timer should be replaced.

The good thing about refrigerators with mechanical defrost timers is the symptoms suggested are mostly characteristic of a problem with the defrost timer. Additionally, these timers are fairly easy to troubleshoot, and repair or replace, without the need to call freezer repair services. If repairing or replacing the defrost timer does not remedy the cooling problem, or there is reason to suspect some other issue, an appliance owner should schedule appliance repair services with a reputable appliance repair shop!

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