Carrier 48TF004-007 - Manual (Page 44)

44
TROUBLESHOOTING
Table 32 — LED Error Code Service Analysis
LEGEND
Table 33 — Heating Service Analysis
PROBLEM CAUSE REMEDY
Hardware failure.
(LED OFF) Loss of power to control module (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 overload 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 name-
plate information.
Ignition lockout.
(LED 5 flashes) Unit unsuccessfully attempted ignition for
15 minutes. Check ignitor and flame sensor electrode spacing, gaps, etc.
Ensure that flame sense and ignition wires are properly termi-
nated. 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 con-
nection: 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 soft-
ware or hardware. If error code is not cleared by resetting unit power, replace the
IGC.
If the IGC must be replaced, be sure to ground yourself to dissi-
pate 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 additional troubleshooting analysis.
IGC — Integrated Gas Unit Controller
LED — Light-Emitting Diode
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.
Miswired or loose connections. Check all wiring and wire nut 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. Use high speed tap, increase fan speed, or install optional blower, as
suitable for individual units.
Limit switch cycles main burners. Check rotation of blower, thermostat heat anticipator settings, and tem-
perature rise of unit. Adjust as needed.
Too much outdoor air. Adjust minimum position.
Check economizer operation.
Poor flame characteristics. Incomplete combustion (lack of combus-
tion air) results in:
Aldehyde odors, CO, 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 man-
ifold 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 re-
set power to unit.