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TROUBLESHOOTING
Table 18 — LED Error Code Service Analysis
PROBLEM CAUSE REMEDY
Hardware failure.
(LED Off)
Loss of power to IGC. Check 5-amp fuse on IGC, power to unit, 24-v circuit breaker, and
transformer. Units without a 24-v circuit breaker have an internal over-
load in the 24-v transformer. If the overload trips, allow 10 minutes for
automatic reset.
Limit switch fault.
(LED 2 Flashes)
High-temperature limit switch
is open.
Check the operation of the indoor (evaporator) fan motor. Ensure that
the supply-air temperature rise is in accordance with the range on the
unit nameplate.
Flame sense fault.
(LED 3 Flashes)
The IGC sensed flame that
should not be present.
Reset unit. If problem persists, replace control board.
4 consecutive limit switch trips.
(LED 4 Flashes)
Inadequate airflow to unit. Check operation of indoor (evaporator) fan motor and that supply-air
temperature rise agrees with range on unit nameplate information.
Ignition lockout.
(LED 5 Flashes)
Unit unsuccessfully attempted
ignition for 15 minutes.
Check ignitor and flame sense electrode spacing, gas, etc. Ensure that
flame sense and ignition wires are properly terminated. Verify that unit
is obtaining proper amount of gas.
Induced-draft motor fault.
(LED 6 Flashes)
IGC does not sense that
induced-draft motor is operating.
Check for proper voltage. If motor is operating, check the speed sensor
plug/IGC Terminal J2 connection. Proper connection: PIN 1-White,
PIN 2-Red, PIN 3-Black.
Rollout switch fault.
(LED 7 Flashes)
Rollout switch has opened. Rollout switch will automatically reset, but IGC will continue to lock out
unit. Check gas valve operation. Ensure that induced-draft blower
wheel is properly secured to motor shaft. Reset unit at unit disconnect.
Internal control fault.
(LED 8 Flashes)
Microprocessor has sensed an
error in the software or hardware.
If error code is not cleared by resetting unit power, replace the IGC.
LEGEND
IGC — Integrated Gas Unit Controller
LED — Light-Emitting Diode
WARNING: If the IGC must be replaced, be sure to ground
yourself to dissipate any electrical charge that may be present
before handling new control board. The IGC is sensitive to static
electricity and may be damaged if the necessary precautions are
not taken.
IMPORTANT: Refer to Table 19 — Heating Service Analysis for ad-
ditional troubleshooting analysis.
Table 19 — Heating Service Analysis
PROBLEM CAUSE REMEDY
Burners will not
ignite.
Misaligned spark electrodes. Check flame ignition and sensor electrode positioning. Adjust as needed.
No gas at main burners. Check gas line for air, purge as necessary. After purging gas line of air, allow gas
to dissipate for at least 5 minutes before attempting to relight unit.
Check gas valve.
Water in gas line. Drain water and install drip leg to trap water.
No power to furnace. Check power supply, fuses, wiring, and circuit breaker.
No 24 v power supply to
control circuit.
Check transformer. Transformers with internal overcurrent protection require a cool
down period before resetting. Check 24-v circuit breaker, reset as necessary.
Miswired or loose connections. Check all wiring and wirenut connections.
Burned-out heat anticipator in
thermostat.
Replace thermostat.
Broken thermostat wires. Run continuity check. Replace wires, if necessary.
Inadequate heating. Dirty air filter. Clean or replace filter as necessary.
Gas input to unit too low. Check gas pressure at manifold. Clock gas meter for input. If too low, increase
manifold pressure, or replace with correct orifices.
Unit undersized for application. Replace with proper unit or add additional unit.
Restricted airflow. Clean filter, replace filter, or remove any restrictions.
Blower speed too low. Install field-supplied motor and drive or adjust pulley to increase fan speed.
Limit switch cycles main burners. Check rotation of blower, thermostat heat anticipator settings, and temperature rise
of unit. Adjust as needed.
Too much outdoor air. Adjust minimum position.
Check economizer operation.
Poor flame
characteristics.
Incomplete combustion (lack of
combustion air) results in:
Aldehyde odors, carbon monoxide,
sooting flame, or floating flame.
Check all screws around flue outlets and burner compartment. Tighten as
necessary.
Cracked heat exchanger.
Overfired unit — reduce input, change orifices, or adjust gas line or manifold
pressure.
Check vent for restriction. Clean as necessary.
Check orifice to burner alignment.
Burners will not
turn off.
Unit is locked into Heating mode
for a one minute minimum.
Wait until mandatory one minute time period has elapsed or reset power to unit.
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