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SERVICE PROCEDURE RG-VIII
Resettable Thermal Switch
Testing and Replacement
RESETTABLE THERMAL SWITCH CONTINUITY TESTING
Step 1.
Step 2.
Remove the outer jacket door.
Disconnect the wire leads from the 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.
Step 5.
If continuity is indicated, the switch is closed, allowing millivolt current to pass.
If continuity is not indicated, the switch is open, possibly due to an overheating condition. The
switch is designed to open at predetermined temperatures depending on model. 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 heater back in service.
PROBABLE CAUSE FOR RESETTABLE THERMAL SWITCH
ACTIVATION
PROBABLE CAUSE
PROBABLE CAUSE
Insufficient combustion air
1.
Verify adequate
combustion air supply is
available.
2.
Clear jacket slot openings
of any dirt, dust,
restrictions or other
obstructions.
3.
Inspect flame arrestor plate
and clean with a stiff brush,
compressed air to remove
scale deposits and debris.
1.
Weak switch or switch out
of calibration.
2.
Incorrect switch.
1.
Replace resettable thermal
switch.
2.
Verify switch color code
and approximate
temperature.
Flammable vapor incident
1. Replace water heater.
Resettable thermal switch color
code reference
Color code
Approximate
switch
activation
temperature
(open)
Blue
Û
Yellow
Û
Red
Û
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