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D. Thermistor Check
The cabinet thermistor works in conjunction with cabinet temperature control dial (CTCD)
to control cabinet temperature. The defrost thermistor is used for defrost initiation and
termination on all models and evaporator fan motor restart on UF/WF.
• UR/WR: Defrost termination is 45°F (7.2°C).
• SR: Defrost termination is 46°F (7.7°C).
• UF/WF: Defrost initiation is below -31°F (-35°C).
Defrost termination is 55°F (12.7°C).
• UR/WR: Evaporator fan motor is energized during defrost.
• SR and UF/WF: Evaporator fan motor de-energized during defrost.
UF/WF Only; Evaporator fan motor is delayed until defrost thermistor achieves
10°F (-12.2°C) or 3-min. EvapFM delay timer terminates after defrost termination.
Thermistor resistance varies depending on temperature. The control module monitors the
thermistors and cabinet temperature control dial (CTCD) to control system operation.
No adjustment is required.
To check thermistor resistance, follow the steps below.
1) Unplug the appliance from the electrical outlet.
2) Remove the evaporator shroud and rear louver.
3) Disconnect the thermistor connector from the control module.
4) Remove the thermistor in question, then immerse the thermistor sensor portion in a
glass containing ice and water for 2 to 3 min.
5) Check the resistance between the wires at the thermistor connector. Normal reading
is within 268.0 kΩ (39°F (4°C)) to 313 kΩ (34°F (1°C)). If outside the normal reading,
replace the thermistor.
6) Reconnect and replace the thermistor and thermistor connector in their correct
positions. Note: After working with or around the defrost thermistor on an SR or UF/WF,
make sure the defrost thermistor wire is not touching the defrost heater.
7) Replace the evaporator shroud and rear louver. Plug the appliance back in to the
electrical outlet.
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