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Determine failure mode by observing flashing LED status on ignition module.
LED status and probable cause shown below.
* Denotes conditions that may require the water heater to be isolated from the vent
system to determine root cause.
LED status & probable cause
For models with Hot Surface Ignition
LED STATUS
Power & flame
light flashing.
Probable Cause
Supply voltage
polarity.
LED STATUS
Valve light flashing.
Probable Cause
Flame sensor.
(see “Flame Sensor
Testing and Replacement”)
Probable Cause
Hot surface igniter.
(see “Hot Surface
Igniter Testing and
Replacement”)
Probable Cause*
Combustion system.
(see “Combustion
System Testing and
Replacement”)
Probable Cause*
Intake pressure switch. Only for
models prior to CF serial number
(see “Intake Pressure Switch
Testing and Replacement”)
Probable Cause
Blower.
(see “Blower Testing
and Replacement”)
Probable Cause*
Exhaust pressure
switch. (see “Exhaust
Pressure Switch
Testing and
Replacement”)
LED STATUS
Purge light flashing.
LED STATUS
Only power light
is on and water heater
will not function.
Probable Cause
Thermostat circuit.
(see “Thermostat Circuit
Testing and Replacement”)
Probable Cause*
Exhaust pressure
switch. (see “Exhaust
Pressure Switch
Testing and
Replacement”)
Probable Cause
Vent safety switch.
(see “Vent Safety Switch
Testing and Replacement”)
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