Ignition Control Board Diagnostic Codes - Lennox G40UH Series Installation Instructions Manual

Ignition Control Board Diagnostic Codes

LED #1 (Red) LED #2 (Green)
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
FAST FLASH
SLOW FLASH
OFF
ALTERNATING
SLOW FLASH
SLOW FLASH
ON
ON
ON
OFF
FAST FLASH
SLOW FLASH
ALTERNATING
FAST FLASH
NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
Minimum flame sense current = 0.5 microAmps.
DIAGNOSTIC CODES
Make sure to Identify LED'S Correctly.
Refer to figure NO TAG for control board layout.
Power on − Normal operation.
SIMULTANEOUS
Also signaled during cooling and continuous fan.
SLOW FLASH
SIMULTANEOUS
Normal operation − signaled when heating demand initiated at thermostat.
FAST FLASH
Primary or secondary limit switch open. Limit must close within 3 minutes or unit
ON
goes into 1 hour Watchguard.
Pressure prove switch open.
SLOW FLASH OR: Blocked inlet/exhaust vent;
OR: Pressure switch closed prior to activation of combustion air inducer.
Watchguard −− burners failed to ignite or lost flame 5 times during single heating
ALTERNATING
demand.
SLOW FLASH
OFF Flame sensed without gas valve energized.
SLOW FLASH Rollout switch open. OR: 12-pin connector improperly attached.
ON
Circuit board failure or control wired incorrectly.
OFF
ON
SLOW FLASH Main power polarity reversed. Switch line and neutral.
FAST FLASH Low flame signal. Measures below 1.5 microamps. Replace flame sense rod.
Improper main ground.
ALTERNATING
OR: Line voltage below 90 volts.
FAST FLASH
DESCRIPTION
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