17
Thermostat Circuit Testing and Replacement
IMPORTANT NOTE:
This procedure assumes a cool tank.
120 volt potential exposure. Use caution making
voltage checks to avoid personal injury.
WARNING
Use caution not to damage connectors when
making voltage measurements or jumping
terminals
CAUTION
Condition: Water heater not operating.
Display shows error code “93” (sensor
reading faulty)
N
Unplug or disconnect electrical power to the water heater.
Check continuity of wire harness to sensor. Resistance of
harness should be close to 0 ohms. Replace wire harness
if high resistance is measured (over .5 ohms). Check
wires for intermittent connections, shorts, frayed
insulation. Replace if necessary.
If wire harness is O.K., check sensor resistance detailed
in “Appendix – A: sensor resistance at various
temperatures” at the end of the thermostat testing and
replacement section. Replace sensor if needed.
Turn power ON to water heater. Run water heater through
heating cycle and verify proper operation. Sensor
temperature can be viewed when burner shuts off (see
section on viewing the display in “Service Mode”).
Condition: Water heater not operating. Display
shows error code “80” high water temperature
(over 200 °F).
WARNING
Do not reset the display from the hard lockout
state without correcting the cause of the
overheating condition.
Turn power OFF. Draw water to cool tank below 120 °F
Check sensor. Sensor is held in place with a clip fastened
to the well (see photo). Check sensor wire for potential
damage or breaks in the wire insulation. Is the sensor fully
inserted into the well?
If sensor clip is damaged replace
clip. Replace sensor if damaged.
Check sensor resistance (see Sensor
Resistance Testing, following section).
Continued on
next page.
Y
Checking
continuity of
sensor
(disconnected
from control board.
Sensor shown fully
inserted into well
Sensor clip shown
properly installed
17
