Bradford White EF120T4003NA3 Service Manual page 22

Thermostat Circuit Testing and Replacement
IMPORTANT NOTE: This procedure assumes a cool tank.
Condition: Water heater not operating. Digital display
shows error code 93 (sensor reading faulty).
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, and/or frayed
insulation. Replace if necessary.
If wire harness is O.K., check sensor resistance detailed in
Appendix A: Sensor Resistance at Various Temperatures,
pg 21. 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 digital display in Service Mode).
Condition: Water heater not operating. Digital
display shows error code 80 high water
temperature (over 207°F).
DO NOT reset the digital 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 image). Check sensor wire for potential
damage or breaks in the wire insulation. Is the sensor fully
inserted into the well?
22
Service Procedure I:
WARNING
120 volt potential exposure. Use caution
making voltage checks to avoid personal injury.
Use caution to NOT damage connectors when
making voltage measurements or jumping
Checking continuity
of sensor across
the two black wires
(disconnected from
control board)
Sensor clip shown
properly installed
The sensor is located next to the top outlet location
If sensor clip is damaged replace
clip. Replace sensor if damaged.
N
Check sensor resistance (see Appendix
A: Sensor Resistance, pg 21).
Y
22
WARNING
CAUTION
terminals.
Continued on
next page.