Carrier 48TC series, Service And Maintenance Instructions, Page: 45 / 112

45
LEGEND
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 19 — 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.
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.
Check/clean return air filters.
Check burner assembly manifold pressure
to ensure proper firing rate.
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. The minimum
flame sensing microamps is 0.5 mA.
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.
Check to ensure Hall Effect wires are not
rubbing against cabinet sheet metal.
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 24V power, replace the IGC.
Check gas valve connections to IGC
terminals. BRN lead must be on Pin 11.
Check that W1, W2, and Com are correctly
connected to the gas valve terminals.
9 Flashes
Temporary Software
Lockout
No gas heating.
1 hour auto reset, or power
reset.
Electrical interference is disrupting the IGC
software.
IGC
— Integrated Gas Unit Control
LED — Light-Emitting Diode