46
NOTES:
1. There is a 3 second pause between alarm code displays.
2. If more than one alarm code exists, all applicable alarm codes will
be displayed in numerical sequence.
3. Alarm codes on the IGC will be lost if power to the unit is interrupted.
Table 22 — IGC Board LED Alarm Codes
LED
FLASH
CODE
DESCRIPTION
ACTION TAKEN BY
CONTROL
RESET METHOD PROBABLE CAUSE
On Normal Operation — — —
Off Hardware Failure No gas heating. —
Loss of power to the IGC. Check 5 amp fuse
on IGC, power to unit, 24V circuit breaker,
transformer, and wiring to the IGC.
1 flash
Indoor Fan On/Off Delay
Modified
5 seconds subtracted
from On delay.
5 seconds added to Off
delay (3 min max).
Power reset.
High temperature limit switch opens during
heat exchanger warm-up period before fan-on
delay expires.
High temperature limit switch opens within
10 minutes of heat call (W) Off.
See Limit Switch Fault.
2 flashes Limit Switch Fault
Gas valve and igniter
Off.
Indoor fan and inducer
On.
Limit switch closed, or heat
call (W) Off.
High temperature limit switch is open. Check
the operation of the indoor (evaporator) fan
motor.
Ensure that the supply-air temperature rise is
within the range on the unit nameplate. Check
wiring and limit switch operation.
3 flashes Flame Sense Fault
Indoor fan and inducer
On.
Flame sense normal.
Power reset for LED reset.
The IGC sensed a flame when the gas valve
should be closed. Check wiring, flame sensor,
and gas valve operation.
4 flashes
Four Consecutive Limit
Switch Fault
No gas heating.
Heat call (W) Off.
Power reset for LED reset.
4 consecutive limit switch faults within a single
call for heat. See Limit Switch Fault.
5 flashes Ignition Fault No gas heating.
Heat call (W) Off.
Power reset for LED reset.
Unit unsuccessfully attempted ignition for
15 minutes. Check igniter and flame sensor
electrode spacing, gaps, etc. Check flame
sense and igniter wiring. Check gas valve
operation and gas supply.
6 flashes Induced Draft Motor Fault
If heat off: no gas
heating.
If heat on: gas valve Off
and inducer On.
Inducer sense normal, or
heat call (W) Off.
Inducer sense On when heat call Off, or
inducer sense Off when heat call On. Check
wiring, voltage, and operation of IGC motor.
Check speed sensor wiring to IGC.
7 flashes Rollout Switch Lockout
Gas valve and igniter
Off.
Indoor fan and inducer
On.
Power reset.
Rollout switch has opened. Check gas valve
operation. Check induced-draft blower wheel is
properly secured to motor shaft.
8 flashes Internal Control Lockout No gas heating. Power reset.
IGC has sensed internal hardware or software
error. If fault is not cleared by resetting 24 v
power, replace the IGC.
9 flashes
Temporary Software
Lockout
No gas heating.
1 hour auto reset, or power
reset.
Electrical interference is disrupting the IGC
software.
LEGEND
IGC — Integrated Gas Unit Control
LED — Light-Emitting Diode
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