Before you can repair the fridge, you first must understand how the evaporator coils work. Coolant is pumped from the compressor unit through the evaporator coils, which are behind the back panel in the freezer compartment of Kenmore refrigerators. As the coolant moves through the coils, it changes into gas, resulting in low temperatures. Over time, the surface of the coils develops frost and ice. To prevent ice buildup, a heater located under the coils warms up the coils every six to eight hours. This heater is controlled by a timer or circuit board and monitored by a thermostat.
Testing the Defrost Timer
Some Kenmore refrigerators contain timers that control the self-defrosting heaters. Unfortunately, it can be hard to find the timer, depending on the model of your refrigerator. In most cases, side-by-side refrigerators that have temperature control knobs at the top of the fridge compartment often have the defrost timer located near the thermostat behind the control knobs. It looks like a small, round object with one flat end that has four electrical prongs. It is also often located in the control panel, behind the fridge or behind the foot kick panel at the base of the appliance. Use a flathead screwdriver to advance the timer until you hear a click. This should start the defrost heater. If it doesn't, the timer probably needs to be replaced. Continue to turn it clockwise and a second click will be heard, which turns off the defrost heater. If the timer isn't clicking, simply pull it out and "plug in" a new timer.
Testing the Control Panel
Kenmore refrigerators that don't have timers have control panels that control the self-defrosting unit instead. The control panel can sometimes be tested using the controls on the water dispenser or by removing the rear of the front panel to access the controls. A simple press of the button will run several diagnostics that will test your defrost timer, thermostat and heater. The specific instructions vary depending on the model of your Kenmore refrigerator. Consult your owner's manual to run the diagnostics if you have a control panel in your refrigerator.
Calling a Professional
If your coils are icing up, it's not the coils that need to be repaired, but the self-defrosting unit. If the timer is malfunctioning, you can test and replace it yourself. If it's the heater or thermostat, it probably requires repair or replacement by a certified appliance repairman.