Thermostat Circuit Testing - Bradford White D Series Service Manual

120 volt exposure. To avoid personal injury,
use caution while performing this procedure.
This procedure assumes the flue damper is in working order. Be sure damper opens under its own power when the
thermostat circuit is by-passed. Damper must be open or removed during this test. Do not force damper open using your
hands or tools.
Condition: Water Heater Not Operating
Display shows error code "31" (Upper Sensor
Readings Faulty) or error code "32" (Lower Sensor
Readings Faulty)
Unplug or disconnect electrical power to the water heater
Check continuity of wire harness to affected sensor. Measurement
of ohmeter should be close to 0 ohms. Replace wire harness if high
resistance is measured (over 0.5 ohms) Check wires for intermittent
connections, shorts, frayed insulation. Replace if necessary
If wire harness checks out O.K.check resistance of sensor. Refer to
section on Sensor Resistance Testing. If sensor resistance is not
near the values shown in the table, then replace upper or lower
sensor as indicated by error code number.
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 "65"
High Water Temperature (over 200 deg. F)
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 deg. F
Check lower sensor. Is the sensor fully inserted into the well?
Sensor is held in place with a clip fastened to the well (see photo 9)
Check lower sensor wire making sure it is not damaged or has
breaks in the wire insulation. Check upper harness wires to upper
sensor, if used (some models).
24
DANGER
(see photo 8)
WARNING!
SERVICE PROCEDURE D24-I

Thermostat Circuit Testing

Be Careful When Making Voltage
Measurements or Jumping Terminals
Not to Damage or Deform Connectors or
Connector Pins.
If sensor clip is damaged
N
replace clip. Replace lower
sensor if damaged.
Check Sensor Resistance
Y
(see "Sensor Resistance
Testing" section & photo 7)
Page 24
CAUTION
Measuring upper
7
sensor resistance
through wire
harness
(disconnected at
control board).
Checking
8
continuity of
upper sensor wire
harness.
Removing lower
9
sensor from well.
Held in place by a
clip fastened to
well shoulder.
See next page