Carrier 48VT(N) Troubleshooting Guide-Heating, Troubleshooting Guide-LEDStatus Codes, 48VT--A

48VT-- A

Table 12 – Troubleshooting Guide–Heating

SYMPTOM	CAUSE		REMEDY
	Water in gas line	Drain. Install drip leg.
	No power to furnace	Check power supply fuses, wiring or circuit breaker.
		Check transformer.
	No 24--v power supply to control circuit	NOTE: Some transformers have internal over--current protection
		that requires a cool--down period to reset.
Burners will not ignite
	Mis--wired or loose connections	Check all wiring and wire nut connections
	Misaligned spark electrodes	Check flame ignition and sense electrode positioning.
		Adjust as necessary.
		1.	Check gas line for air. Purge as necessary. NOTE: After purging
	No gas at main burners	gas line of air, wait at least 5 minutes for any gas to dissipate be-
		fore attempting to light unit.
		2.	Check gas valve.
	Dirty air filter	Clean or replace filter as necessary
	Gas input to furnace too low	Check gas pressure at manifold match with that on unit nameplate
Inadequate heating	Unit undersized for application	Replace with proper unit or add additional unit
	Restricted airflow	Clean or replace filter. Remove any restriction.
	Limit switch cycles main burners	Check rotation of blower, temperature rise of unit. Adjust as neces-
		sary.
		1.	Tighten all screws around burner compartment
		2.	Cracked heat exchanger. Replace.
	Incomplete combustion results in: Aldehyde odors,	3.	Unit over--fired. Reduce input (change orifices or adjust gas line
Poor flame characteristics		or manifold pressure).
	carbon monoxide, sooting flame, floating flame
		4.	Check burner alignment.
		5.	Inspect heat exchanger for blockage. Clean as necessary.

Table 13 – Troubleshooting Guide–LED Status Codes

SYMPTOM		CAUSE	REMEDY
			Check 5--amp fuse son IGC*, power to unit, 24--v circuit breaker,
No Power Hardware failure		Loss of power to control module (IGC)*.	and transformer. Units without a 24--v circuit breaker have an
(LED OFF)			internal overload in the 24--v transformer. If the overload trips,
			allow 10 minutes for automatic reset.
Limit switch faults			Check the operation of the indoor (evaporator) fan motor. Ensure
		High temperature limit switch is open.	that the supply--air temperature rise is in accordance with the
(LED 2 flashes)
			range on the unit nameplate. Clean or replace filters.
Flame sense fault		The IGC* sensed flame that should not be present.	Reset unit. If problem persists, replace control board.
(LED 3 flashes)
4 consecutive limit switch			Check the operation of the indoor (evaporator) fan motor and that
faults		Inadequate airflow to unit.	supply--air temperature rise agrees with range on unit nameplate
(LED 4 flashes)			information.
Ignition lockout			Check ignitor and flame sensor electrode spacing, gaps, etc.
		Unit unsuccessfully attempted ignition for 15 minutes.	Ensure that fame sense and ignition wires are properly terminated.
(LED 5 flashes)
			Verify that unit is obtaining proper amount of gas.
			Verify wiring connections to pressure switch and inducer motor.
Pressure Switch motor fault			Verify pressure switch hose is tightly connected to both inducer
		Open pressure switch.	housing and pressure switch. Verify inducer wheel is properly
(LED 6 flashes)
			attached to inducer motor shaft. Verify inducer motor shaft is turn-
			ing.
			Rollout switch will automatically reset, but IGC* will continue to
Rollout switch fault		Rollout switch has opened.	lockout unit. Check gas valve operation. Ensure that induced--draft
(LED 7 flashes)			blower wheel is properly secured to motor shaft. Inspect heat
			exchanger. Reset unit at unit disconnect.
Internal control fault		Microprocessor has sensed an error in the software	If error code is not cleared by resetting unit power, replace the
(LED 8 flashes)		or hardware.	IGC*.
Temporary 1 hr auto reset		Electrical interference impeding IGC software	Reset 24--v. to control board or turn thermostat off, then on again.
(LED 9 flashes)			Fault will automatically reset itself in one (1) hour.
*WARNING	: If the IGC must be replaced, be sure to ground yourself to dissipate any electrical charge that my be present before handling new control

board. The IGC is sensitive to static electricity and my be damaged if the necessary precautions are not taken. IMPORTANT: Refer to Table 12---Troubleshooting Guide---Heating for additional troubleshooting analysis.

LEGEND

IGC—Integrated Gas Unit Controller

LED—Light---Emitting Diode

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