York, Coleman Furnace Error Codes
Look up error codes to identify furnace problems and estimate repair costs.
Locating the furnace error code
Refer to the furnace glossary if you need help identifying furnace parts or terms.
All high-efficiency furnaces and most mid-efficiency furnaces show error codes on the control board, either as a flashing LED sequence or on a display .
Where to find the control board and inspection port
The furnace control board is almost always in the lower compartment. You can view the error code LED or display through a small, clear plastic inspection port in the centre of the lower furnace cover.
If the control board isn’t in the lower compartment, it’s in the upper compartment.
How to access the inspection port
Furnaces with upper and lower furnace covers — The inspection port is usually on the lower furnace cover and is accessible without removing the cover.
Furnaces with a one-piece front cover — Remove the front cover first. The inspection port is usually on the secondary cover for the lower compartment.
If the control board is in the upper compartment — You need to remove the upper furnace cover. If there are thumb screws, loosen them and pull the cover out from the screw location. If there are no screws, slide the cover straight up, then pull it out.
Error codes
Don’t turn off the power to the furnace while troubleshooting — unless instructed otherwise. Turning off the power clears the current error code.
Observe the flashing LED sequence or display code, which may repeat in a loop. Watch it carefully, make note of the sequence or digits, and match it up with the corresponding code below:
LED off
No power. Continue to the Power diagnostic →
Slow green flashing
Normal operation, no call for heat. Continue to the Thermostat diagnostic →
Slow amber flashing
Normal operation, calling for heat. Continue to the Secondary diagnostic →
4 amber flashes
Improper thermostat wiring. Possible faulty wiring or thermostat. Book a professional repair.
LED red, not flashing
Faulty control board. Book a professional repair.
Rapid red flashing
Twinning error, incorrect 24V phasing. Possible wiring problem. Book a professional repair.
1 red flash
Flame sensed with gas valve closed. Faulty gas valve or control board. Book a professional repair or continue to the Gas valve diagnostic →
2 red flashes
Pressure switch stuck in closed position. Faulty pressure switch or control board. Book a professional repair.
3 red flashes
Pressure switch stuck in open position. Continue to the Secondary diagnostic →
4 red flashes
Limit switch open. Continue to the Secondary diagnostic →
5 red flashes
Roll out switch open. Blocked exhaust or secondary heat exchanger, or faulty inducer motor. Book a professional repair or continue to the Roll out switch diagnostic →
6 red flashes
Locked out on pressure switch error. Continue to the Secondary diagnostic →
7 red flashes
Locked out on too many ignition attempts. Continue to the Secondary diagnostic →
8 red flashes
Locked out on repeated power cycles. Continue to the Secondary diagnostic →
9 red flashes
Grounding or polarity issue. Possible faulty control board. Book a professional repair.
10 red flashes
Gas continues to flow with gas valve closed. Possible faulty gas valve. Book a professional repair or continue to the Gas valve diagnostic →
11 red flashes
Limit switch open for more than five minutes. Possible faulty blower motor. Book a professional repair or continue to the Blower motor diagnostic →
12 red flashes
Open igniter circuit. Faulty wiring or igniter. Book a professional repair or continue to the Igniter diagnostic →
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