Planned Service; Ignition Control Board Diagnostic Codes - Lennox G43UF Installation Instructions Manual

Planned Service

A service technician should check the following items dur-
ing an annual inspection. Power to the unit must be shut off
for safety.
Fresh air grilles and louvers (on the unit and in the room
where the furnace is installed) − Must be open and unob-
structed to provide combustion air.
Burners − Must be inspected for rust, dirt, or signs of water.
Vent pipe − Must be inspected for signs of water, cracked,
damaged or sagging pipe, or disconnected joints.
Unit appearance − Must be inspected for rust, dirt, signs
of water, burnt or damaged wires, or components.
Blower access door − Must be properly in place and pro-
vide a seal between the return air and the room where the
furnace is installed.

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.
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
Return air duct − Must be properly attached and provide
an air seal to the unit.
Operating performance − Unit must be observed during
operation to monitor proper performance of the unit and the
vent system.
Combustion gases − Flue products must be analyzed and
compared to the unit specifications.
Problems detected during the inspection may make it nec-
essary to temporarily shut down the furnace until the items
can be repaired or replaced.
Instruct the homeowners to pay attention to their
furnace. Situations can arise between annual furnace in-
spections that may result in unsafe operation. For instance,
items innocently stored next to the furnace may obstruct
the combustion air supply. This could cause incomplete
combustion and the production of carbon monoxide gas.
DESCRIPTION
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