– 23 –Evaporator Thermistor
The evaporator thermistor is mounted on the
upper left side of the evaporator. The defrost
cycle will terminate when the main control board
detects 38 °F from the evaporator thermistor. The
main control board must sense 38 °F in less than
35 minutes, or the defrost cycle will time out.
Average time to defrost is less than 16 minutes.
Defrost time should not exceed 35 minutes.
Defrost time does not include dwell period.
Defrost Overtemperature Thermodisc
The defrost overtemperature thermodisc (bimetal
switch) is mounted on the evaporator and
provides overtemperature protection during
defrost. This thermostat will open at 60 °F and
will close at 45 °F.
Note: The main control board will not know if the
heater does not come on due to a broken heater,
open defrost overtemperature thermodisc, or
open wiring harness. The defrost heater is
controlled by maximum time on the main control
board or temperature at the evaporator thermistor.
Evaporator
Thermistor
Defrost
Overtemperature
Thermodisc