Bradford White EF120T4003N3 Service Manual page 18

High limit
80 (overheat
condition)
DHW/Temp
93
sensor fault
Flame
detected
105
out of
sequence
Ignition
110 failure
occurred
Light-off
122 rate proving
failed
Purge rate
123 proving
failed
ILK open
137 (interlock
open)
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Troubleshooting
Check the wiring from the sensor to the control board.
Measure the resistance of each outside wire to the center wire (resistance chart found on
pg 21).
If either outside wire has a much different resistance reading, replace the sensor.
Make sure the sensor is securely held inside the well with the clip.
If the problem persists and the sensor and wiring check O.K., then replace the control
board.
Check the sensor wire harness from the sensor to the control board.
Make sure there are no loose connections to the control board.
Check the resistance reading from each of the outside wires to the center (common) wire
(resistance chart on pg 21).
If the ohm readings are not within 5°F, replace the sensor.
Replace the control board if the problem persists and the sensor and wire connections are
not defective.
Check to see if flame is present inside the combustion chamber before or after the ignition
cycle.
If so, check to make sure the gas valve is wired correctly.
Check for voltage at the gas valve connection.
Replace the gas valve if defective.
If no flame is visible outside of the ignition sequence/run cycle, then make sure the flame
sensor is wired to the correct terminal.
Make sure the ignition cable is not crossing the flame sensor wire or ignition ground wires,
and that there is no moisture on the flame sensor.
If problem persists and all other checks have been verified, replace the control board.
Burner failed to light or stay lit after 3 retries.
Hold condition – will reattempt ignition after 15 minute waiting period.
Check gas valve wiring and gas valve operation during the ignition cycle.
If burner lights but quickly goes out, check the flame sensor wire or the flame sensor.
If the flame sensor rod is badly corroded with deposits, clean with sandpaper or replace.
Check the inlet gas supply to make sure the pressure is sufficient and does not drop after
the gas valve opens.
Make sure the combustion blower is operating during the ignition and run cycle.
Check the venting system to make sure the inlet and exhaust terminals and venting
system is not blocked.
If blower speed is not verified from the PWM (Pulse Width Modulation) signal within 5
minutes, the previously described error code 62 changes from a hold condition to this
lockout code condition.
Check the harness and pin terminals for a good connection to the control board.
Replace the blower or control board if the wire harness is good.
Check wiring and correct any potential wiring errors.
Check VFD's (variable-speed fan drive) ability to change speeds.
Change the VFD.
If the fault persists, replace the module.
Check if blocked vent pressure switches or vent limit switch are open.
If all switches check O.K., replace control board.
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