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 .

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.

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. Professional diagnosis required.

LED red, not flashing

Control faulty failure

Faulty control board.

Rapid red flashing

Twinning error, incorrect 24V phasing

Possible wiring problem. Professional diagnosis required.

1 red flash

Flame sensed with gas valve closed

Faulty gas valve or control board.

2 red flashes

Pressure switch stuck in closed position

Faulty pressure switch.

3 red flashes

Pressure switch stuck in open position

Faulty pressure switch, inducer motor, or blocked intake/exhaust.

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. Professional diagnosis required.

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. Professional diagnosis required.

10 red flashes

Gas continues to flow with gas valve closed

Possible faulty gas valve. Professional diagnosis required.

11 red flashes

Limit switch open for more than five minutes

Possible faulty blower motor. Professional diagnosis required.

12 red flashes

Open igniter circuit

Faulty wiring or igniter.

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Furnace repairs should only be performed by a certified technician.

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