Fixing Defrost System
Isolating the Problem
Warm humid air entering the freezer section when you open the door collects on the evaporator coils as frost. In a few days this frost buildup would completely fill the evaporator section. The defrost timer periodically turns the compressor off and energizes the defrost heater. The defrost heater melts the frost and the condensate runs down into the condensate pan under the refrigerator.
Check the defrost heater first by locating the defrost timer under the refrigerator, behind the kick plate or inside the refrigerator behind the temperature control panel. Use a flat blade screwdriver to advance the timer knob clockwise until the compressor stops. This should energize the defrost heater for 15 to 20 minutes. Listen for hissing and popping sounds from the back of the freezer section. Look for condensate dripping into the condensate pan underneath the refrigerator. If the defrost heater seems to work then prepare to replace the timer. If nothing seems to be happening, unplug the refrigerator and start removing the evaporator cover from the rear of the freezer section by removing the icemaker and the screws holding the cover. Pull the evaporator cover foward at the top, up and out from one side to clear the shelf brackets. Look for the black defrost heater under the evaporator coils and up each end of the coils. One of the black wires coming off either end usually burns off. If it is not obvious that the heater has burned in two, put an ohmmeter on each end and confirm that it is not open.
If an open circuit is indicated, replace the defrost heater. There is a defrost thermostat in series with the defrost heater. It should be closed as long as the evaporator coil area is less than 55 deg. F. Though the defrost thermostat is least likely to fail, check it if the timer and heater check out OK but the heater won’t come on.
Replacing the Defrost Heater
Get a new defrost heater element using the model number from your refrigerator. Disconnect both black wires from the other wiring after removing the wire nuts. Release the old element from the mounting clips. Install the new element the same way you removed the old one. Twist the new leads into the same wire bundles that the old one was in and replace the wire nuts. Replace the evaporator cover and the icemaker if you had one.
Replacing the Defrost Timer
A good generic timer is Whirlpool’s 482493. You may have to bend the terminals straight to fit the timer connector.
Make sure the refrigerator is unplugged. Remove the screws holding the defrost timer. The 4 wires to the timer are grouped into a connector. Pull the connector off the old timer and slide it on the new timer. Remount the new timer using the 2 mounting screws. Replace any plastic control covers. This completes the installation of the new timer.
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