Thermistor Check - Hoshizaki Steelheart Series Service Manual

C. Thermistor Check
This appliance utilizes 3 thermistors: Rail thermistor, cabinet thermistor, and defrost
thermistor. The rail thermistor is used for rail temperature control, the cabinet thermistor
is used for cabinet temperature control and the defrost thermistor is used for defrost
termination (41°F (5°C)). The defrost thermistor is also used for evaporator fan motor/
cabinet fan motor initiation after defrost (36°F (2.2°C) or lower). Thermistor resistance
varies depending on temperature. The rail control module monitors the rail and defrost
thermistors, while the cabinet control module monitors the cabinet thermistor.
To check thermistor resistance, follow the steps below.
1) Unplug the appliance.
2) Remove the front panel.
3) Disconnect and remove the thermistor in question.
4) 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. If outside the
normal reading, replace the thermistor.
Cabinet Control Module: 4A7178-01
PR46B: L-5 to M50052H, M50073K and Later; (-D2): ALL
PR60B: L-5 to M50007H, M50025L and Later; (-D4): ALL
PR67B(-D2)(-D4): ALL
PR93B(-D2)(-D4)(-D6): ALL
a) Rail and Defrost Thermistor - 16 to 16.7 kΩ
b) Cabinet Thermistor - 25 to 27 kΩ
Cabinet Control Module: 4A7053-01
PR46B: M50053H-M50072H
PR60B: M50008H-M50024H
a) Rail , Cabinet, and Defrost Thermistor - 16 to 16.7 kΩ
6) Reconnect and replace the thermistor in its correct position.
7) Plug the appliance back in.
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