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American Standard, Trane 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

LED flashing slowly

Normal operation, no call for heat

Continue to the Thermostat diagnostic

LED flashing quickly

Normal operation, furnace should be running or cycling

Continue to the Secondary diagnostic

LED on, not flashing

Control board problem

Possible wiring problem, transformer issue, or faulty control board. Requires professional diagnosis.

2 flashes

Lock out on retries

Continue to the Secondary diagnostic

3 flashes

Pressure switch error

Continue to the Secondary diagnostic

4 flashes

Open limit switch

Continue to the Secondary diagnostic

5 flashes

Flame sensed when gas valve off

Possible faulty gas valve or control board. Requires professional diagnosis.

6 flashes

Line voltage polarity incorrect

Possible wiring, transformer, or control board failure. Requires professional diagnosis.

7 flashes

Gas valve circuit problem

Possible faulty gas valve or control board. Requires professional diagnosis.

8 flashes

Low flame sensor

Faulty flame sensor, igniter, or gas valve.

9 flashes

Igniter problem

Faulty igniter or gas valve.

Error code not listed

Other furnace problem

Continue to the Secondary diagnostic

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Furnace repairs should only be performed by a certified technician.

This website is for informational purposes only. Advanpro Ltd. is not liable for property damage, personal injury, or death caused directly or indirectly by actions taken as a result of the information provided here.

Repair Igniter or Gas Valve

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Repair Flame Sensor, Igniter, or Gas Valve

$199, $379, or $899 + GST

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Professional Diagnosis Required

$109.95 regular hours call-out & diagnosis fee

Our technician will identify the problem and tell you how much it will cost to repair. Once you know the problem and the cost, you can decide if you want to proceed.

(403) 873-7779

Call us 24 hours, 7 days a week

[email protected]

Email us, get a reply in 1 business day