32
Res. D Series
32
Resettable Thermal Switch Continuity Testing
Step 1.
Move the gas control power switch to the
“OFF” position and unplug the water heater
from the wall outlet.
Step 2.
Remove the outer jacket door.
Step 3.
Disconnect the wire leads from the resettable
thermal switch.
Step 4.
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 5.
If continuity Is indicated, the switch is closed,
allowing millivolt current to pass.
Step 6.
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 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.
Probable cause for resettable thermal switch activation
Probable Cause
Corrective Action
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
and/or vacuum to remove
scale deposits and debris.
1.
Weak switch or switch
is out of calibration.
2.
Incorrect switch.
1.
Replace resettable
thermal switch.
2.
Verify switch color code
and approximate
temperature.
Flammable vapor incident
Replace water heater.
Resettable thermal switch color code
reference
Color code
Approximate switch
activation temperature
(open)
Blue 240°
Yellow 270°
Red 290°
