Service Manual

UTTW SERVICE PROCEDURE IX
Resettable Thermal Switch Testing
and Replacement
Step1. Remove outer jacket door.
Step 2.Disconnectredwire leads from resettable thermal switch.
Step3. Using a multimeter capable of measuring con
tinuity(Ohms),
place one probe of meter on one of the brass connection tabs of
the resettable thermal switch, and the remaining probe on the
other connection tab.
Step4. Ifcontinuityi
s indicated, the switch is closed, allowing currenttopass.
Step5. Ifcontinuityis not indicated, the switch is open, possibly due to anover heating condition. The switch is
designed toopen at predetermined
temperatures.Anopen switch canbe reset by depressing the red colored
button located atthe center of the switch. The overheating condition must be determinedpriortoputting the
wa
ter heater back in service.
Resettable Thermal Switch Continuity Testing
PROBABLE CAUSE FOR RESETTABLE THERMALSWITCH ACTIVATION
PROBABLE CAUSE CORRECTIVE ACTION
Burner Failure
1. Inspect burner per SERVICE PROCEDURE II
2. Replace burner per SERVICE PROCEDURE II
Weak switch or switch
out of calibration.
1. Replace resettable thermal switch
Red Wire Leads
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