Repair Parts List; Ignition Control Board Diagnostic Codes - Lennox G50UH Series Installation Instructions Manual

Repair Parts List

The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model
number listed on the CSA International nameplate −− Example: G50UH(X)−24A−045−8. All service must be performed by a
licensed professional installer (or equivalent), service agency, or gas supplier.
Cabinet Parts
Upper access panel
Blower panel
Top cap
Control Panel Parts
Transformer
®
SureLight ignition board
Door interlock switch
Circuit breaker
Blower Parts
Blower wheel
Motor
Motor mounting frame
Motor capacitor
Blower housing cutoff plate

Ignition Control Board Diagnostic Codes

DS1
(Red or 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).
Drop out flame sense current = 0.15 − 0.24 microAmps.
DIAGNOSTIC CODES
Make sure to Identify LED'S Correctly.
Refer to Installation Instructions for control board layout.
DS2
(Green)
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 switch open;
OR: Blocked inlet/exhaust vent;
SLOW FLASH
OR: Condensate line blocked;
OR: Pressure switch closed prior to activation of combustion air inducer.
Watchguard −− Burners failed to ignite, limit open longer than 3 minutes, or flame
ALTERNATING
sense lost 5 times in one heating cycle.
SLOW FLASH
OFF Flame sensed without gas valve energized.
SLOW FLASH Rollout switch open.
ON
Circ it board fail re or control ired incorrectl Circuit board failure or control wired incorrectly. Check 24−volt and 115−volt
OFF
connections to board. connections to board.
ON
SLOW FLASH Main power polarity reversed. Switch line and neutral. Improper main ground.
FAST FLASH Low flame signal. Check flame sensor.
The following conditions are sensed during the ignitor warm−up period only:
1) Improper main ground;
ALTERNATING
2) Broken ignitor; OR: Open ignitor circuit;
FAST FLASH
3) Line voltage below 75 volts.
Heating Parts
Flame Sensor
Heat exchanger assembly
Gas manifold
Combustion air inducer
Gas valve
Main burner cluster
Main burner orifices
Pressure switch
Ignitor
Primary limit control
Flame rollout switch
Secondary limit (not used on 24A−45−1)
DESCRIPTION
Page 35
Check 24 olt and 115 olt
G50UH Series