Bradford White U-TW4-75S-76R-3N - Manual (Page 29)

U TTW SERVICE PROCEDURE IX
Resettable Thermal Switch Testing
and Replacement
Step 1. Remove outer jacket door.
Step 2. Disconnect red wire leads from resettable thermal switch.
Step 3. Using a multimeter capable of measuring continuity (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.
Step 4. If continuity is indicated, the switch is closed, allowing current to pass.
Step 5. If continuity is not indicated, the switch is open, possibly due to an over heating condition. The switch is
designed to open at predetermined temperatures. An open switch can be reset by depressing the red colored
button located at the center of the switch. The overheating condition must be determined prior to putting the
water heater back in service.
Resettable Thermal Switch Continuity Testing
PROBABLE CAUSE FOR RESETTABLE THERMAL SWITCH 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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