Lennox G43UF SERIES Unit Information

Page 11
The integrated ignition control board is equipped with two LED lights for troubleshooting. The diagnostic codes are listed
below in table 4.
TABLE 4
DIAGNOSTIC CODES
Make sure to Identify LED’S Correctly..
LED#1
32M88 − DS1 Green
78M47 − DS1 Red
LED #2
32M88 − DS2 Green
78M47 − DS2 Green
DESCRIPTION
SIMULTANEOUS
SLOW FLASH
SIMULTANEOUS
SLOW FLASH
Power on − Normal operation.
Also signaled during cooling and continuous fan.
SIMULTANEOUS
FAST FLASH
SIMULTANEOUS
FAST FLASH
Normal operation − signaled when heating demand initiated at thermostat.
SLOW FLASH ON
Primary or secondary limit switch open. Limit must close within 3 minutes or
unit goes into 1 hour Watchguard.
OFF SLOW FLASH
Prove switch open.
OR:Blocked inlet/exhaust vent;
OR: Prove switch closed prior to activation of combustion air inducer.
ALTERNATING
SLOW FLASH
ALTERNATING
SLOW FLASH
Watchguard −− burners failed to ignite
OR: limit open more than 3 minutes (control board 32M88 Only)
OR: lost flame sense 5 times in one heating cycle
OR: prove switch opened 5 times in one heating cycle
SLOW FLASH OFF Flame sensed without gas valve energized.
ON SLOW FLASH Rollout switch open. OR: 12-pin connector improperly attached.
ON ON
ON OFF
Circuit board failure or control wired incorrectly.
OFF ON
y
FAST FLASH SLOW FLASH Main power polarity reversed. Switch line and neutral.
SLOW FLASH FAST FLASH
Low flame signal. Measures below
Control board 32M88 − 0.18 microamps
Control board 78M47 & 100973−01 − 1.5 microamps
Replace flame sense rod.
ALTERNATING
FAST FLASH
ALTERNATING
FAST FLASH
The following conditions are sensed
Improper main ground (control board 32M88) during the ignitor warm−up period
ONLY Improper main ground (control board 78M47 & 100973−01) continuously
OR: Broken ignitor (control board 32M88)
OR: Open ignitor circuit (control board 32M88)
OR: Line voltage to control below
Control board 32M88 75V
Control board 78M47 & 100973−01 90V
NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).
Low flame sense current = SureLight Control Board 32M88 0.16 − 0.17 microamps Ignition Control Board 78M47 & 100973−01 0.5 − 1.4 microamps
FIGURE 5
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉ
ÉÉ
DEMAND
CAI
GAS VALVE
ON
OFF
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉÉ
ÉÉ
ÉÉ
ÉÉÉÉÉÉÉÉÉÉ
ÉÉÉÉÉÉÉÉÉÉ
IGNITOR**
15 Sec.
Pre −Purge
20 sec.
Ignitor Warmup
4 Sec.Trial
for Ignition
Post
Purge
5 SEC
*Blower on time will be 45 seconds after gas valve is energized. Blower off time will depend on OFF TIME" Setting.
INDOOR BLOWER
ÉÉÉÉÉÉÉÉÉ
Blower On"
Delay
End of
Heat Demand
Blower
Off
Time
** Ignitor on ignition control board 78M47 & 100973−01 equipped units will energize for the first 3 seconds of the 4
second trial, following the ignitor 20 second warm up .

Lennox G43UF SERIES Specifications

General

Brand	Lennox
Model	G43UF SERIES
Category	Furnace
Language	English