Whirlpool 1997 F, Service Manual

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7
Defrost System
Automatic defrost every eight hours of compressor run time is accomplished by a radiant electric
heater suspended beneath the evaporator.
(Fig. 4)
The defrost timer is located in a box at the right side of the cabinet behind the toe grille.
(Fig. 5) The
defrost timer actuates the defrost heater through the bi-metal thermostat. (Fig. 6)
The bi-metal thermostat is attached to the outlet side of the evaporator coil tubing and opens at 48°F
to terminate the defrost heating. After 33 minutes from the start of defrost cycle, the timer restores
operation to the compressor circuit. The bi-metal thermostat contacts close at 13°F, enabling the
defrost heater to operate during the next defrost cycle. The defrost heater is suspended on the right
side and across the bottom of the evaporator. The defrost heater also provides warming to the
defrost drain area to keep it clear during the defrost cycle.
Retaining
Clip
Retaining
Clip
Defrost Heater
Bi-Metal
Thermostat
Defrost
Timer
Fig. 4
Fig.5
Fig.6
Evaporator