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Caution:
Please read our safety
information before attempting any testing or repairs.
Before testing the defrost timer, unplug the freezer
to avoid an electrical shock hazard.
A mechanical defrost timer controls the defrost
cycle of the appliance. In older models, the timer runs continuously
and roughly every six hours, shuts off power to the cooling
system and sends power to the defrost heater. In newer models
the timer advances only when the compressor or defrost cycle
is running - an improvement for efficiency. As the timer advances,
power to the heating element shuts off and power is restored
to the cooling system. If the timer does not advance, the appliance
will be stuck either in defrost or refrigerate mode, resulting
in, respectively, no cooling or frost
build-up.
The defrost timer is usually found behind the front grill of the freezer. It may also be found behind a cover plate inside the freezer, in the temperature control console, or behind the freezer near the compressor.
To test whether the defrost timer is simply
failing to advance, locate the advance screw and turn it clockwise
until you hear it click. This advances it to the next mode.
If it was cooling before, it is now in defrost mode. Simply
wait about 35 minutes and check whether it has left defrost
mode and has resumed cooling (listen for the compressor). If
it does not advance, the timer motor is probably bad and the
entire timer needs to be replaced. If
it advances as it should, then you can follow the steps below
to test the switch electrically.
The timer is usually held in place with one
or more screws. Remove the screws and gently pull the timer
out far enough to disconnect the wiring connector. The connector can be removed by firmly pulling
and rocking it left and right. It is not necessary to note the
position of the wires because the connector plug is keyed so that
it can be replaced in only one way.
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