Bradford White EF120T4003NA3 Service Manual page 19

SERVICE ERROR CODES AND TROUBLESHOOTING PROCEDURES FOR 120T400/500 MODELS WITH
The ICON control system can produce soft and hard lockouts. Soft lockouts are displayed if active
and are not stored in Diagnostic Mode history. The control will periodically attempt to resume
normal operation when in soft lockout conditions. If the system resumes normal operation a soft
lockout will clear instantly; hard lockouts will display if active and require manual reset. Up to ten
previous Hard lockouts are logged chronologically (newest first) in Diagnostic Mode history.
Definition
Error Code
of Code
No power to
No code –
the unit or
blank
switch is
display
off.
Low flame
9,22 sense
signal
Voltage too
49
low or high
AC Inputs
53 phase
reversed
Fan speed
62
not proved
Normally
closed vent
67 safety
circuit
opened
Troubleshooting
RESIDEO LOW FIRE START CONTROL SYSTEM
NOTICE
Cause of Problem and Actions Taken to Correct
• Check power supply to the water heater.
• Make sure water heater is plugged in and the breaker is on.
• Check if there is 120 volts power supply to the LINE connections on the control
board.
• Verify 24 volts at display.
• Check for loose wires, defective transformer.
• Check wire harness connections from display to the control board.
• Check microamp output of flame sense
• Inspect flame sensor and wire
• Inspect burner for debris
• Measure the incoming line voltage.
• Voltage should be 115-125 volts.
• If the voltage is not within this range or there is drastic fluctuation, then have the
incoming power supply checked.
• If the line voltage is satisfactory, check the output from the transformer to make sure
it is 22-26 volts.
• Replace transformer or wiring if defective.
• Check the module and display connections.
• Check the module power supply and make sure that frequency, voltage and VA
capacity of the transformer meet specifications.
• Check to make sure the wiring connections on the control module from terminals J4-
10 and J8-2 are connected together.
• Check the pulse width modulation (PWM) wire harness connection from the blower to
the control module.
• Make sure the pin terminals make solid contact.
• Measure the resistance of each wire in the wire harness from the terminal ends.
• Replace wire harness if defective.
• If value remains out of range, this hold will change to lockout 123 (defined below)
• Check wiring to the normally closed blocked vent pressure switch and vent limit
switch.
• Use a voltmeter to find out if either the pressure switch or the high limit switch has
opened.
• If so, determine the cause (blocked vent terminal, clogged condensate drain, high
temperature in compartment).
• If limit switches are closed, check wiring for shorts.
• Measure continuity.
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