DV Series
37
Resettable Thermal Switch Continuity Testing
Step 1. Remove the outer jacket door.
Step 2. Disconnect the wire leads from the resettable thermal
switch.
Step 3. Using a multimeter capable of measuring continuity
(ohms), place one probe of the 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 millivolt current to pass.
Step 5. If continuity is not indicated, the switch is open, possibly due to an overheating
condition. The switch is designed to open at a predetermined temperatures
depending on the 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.
Service Procedure VII
Resettable Thermal Switch
Testing and Replacement
PROBABLE CAUSE FOR RESETTABLE THERMAL SWITCH ACTIVATION
PROBABLE CAUSE
SERVICE PROCEDURE
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
240˚
Yellow
270˚
Red
290˚
37
