Furnace error codes by brand: lights, fixes $133 to $505

National figures. The code narrows the fault; the part and the labor set the price.

Do this now: when the furnace light is blinking

1. Smell gas? Leave without touching light switches, phones or the garage door opener, then call 911 or the gas utility from outside (Kansas Corporation Commission). The furnace waits.
2. Carbon monoxide alarm sounding, or anyone dizzy, nauseous or confused? Get everyone outside, then call 911 from outside. CPSC says not to search for the source and not to go back in until responders say it is safe.
3. Look through the sight glass, panel on. Trane says not to take the front panel off while the furnace is running, and that some units have a blower door switch that cuts power and gas when the door is removed.
4. Count the flashes and the pause. Trane's advice: write down the colors, the blink pattern and any letters or numbers.
5. Read the label. The legend for your model is printed inside the blower door. Match the count to it before you do anything.
6. Do the free checks. Filter, open vents, thermostat batteries, the furnace switch (Bryant: the SSU switch on the gray box at the furnace), the breaker. Goodman's manuals reset a lockout by cycling the furnace's power, and say to reset a tripped limit control only once.
7. Same code again? Leave it off and call. Trane: "call for furnace repair now" if it is not igniting or not blowing hot air, and give the scheduler the lights or codes and the brand and model.

Is it an emergency? Codes that mean shut the furnace off

A furnace code is an emergency when it comes with gas, carbon monoxide or heat where it should not be, and the Goodman manuals put a hard rule on the limit and rollout codes (4, 5, 6 and 11 flashes): reset once, and if overheating occurs or the gas supply fails to shut off, turn off the manual gas valve outside the furnace.

• Rollout, overheating or limit codes that return after one reset. Goodman: "Should overheating occur or the gas supply fail to shut off, turn off the manual gas shutoff valve external to the furnace." Then call. Do not reset it a second time.
• Any code plus a burning smell, soot or a CO alarm. Furnace off; see cracked heat exchanger.
• A refrigerant leak code (Goodman EAL). The furnace has already shut the gas off; leave the fan running and call.
• Ignition or flame codes with no heat in freezing weather: emergency HVAC repair.
• Can wait: a code that cleared after one reset and has not returned; book a visit and give them the code.

Furnace flashing red light, blinking green light: what the colors mean

A green light is the furnace talking and a red light is the furnace complaining, in Trane's description: a slow green blink can mean no call for heat, a fast green blink means it is heating, and a blinking red light generally signals a problem.

Trane owner page (Sep 2025); Goodman and Amana service manuals (2023).

Trane lists the problem areas a red pattern can point to: lockout, ignition failure, the high limit switch, the pressure switch, the gas valve, the heat exchanger and the control board. Which one is which depends on the brand, so the next sections go brand by brand and list only what the manufacturer's own documents say.

Goodman furnace error codes and Amana furnace error codes

Goodman and Amana furnaces share control boards, and three Goodman service manuals give the codes below; the manual for the 80% single-stage models warns "Do not bypass any safety circuit" and says to reset the auxiliary limit control only once.

Goodman RS6621301 (Nov 2023), RS6621007r2 (Sep 2023) and RS6612022r1 (Mar 2023). Other flash counts exist on these boards; only the ones the readable text defines are listed.

The newer Goodman and Amana 90%+ boards (GM9S92, GM9S96, GC9S96, AM9S92, AM9S96, AC9S96, VM9S96, VC9S96) show faults on a display and store the last ones: the manual lists failure to establish flame after 3 ignition retries, an open primary limit (check filters and ductwork), flame sensed with no call for heat, a lingering burner flame, an open fuse, a low-voltage short, gas valve errors, no 115 V or 24 V power, an open rollout switch, an open igniter, and inducer relay, TWIN or internal faults that call for a new control board. The code letters for each did not survive our copy of the manual, so they are not printed here; the legend on the furnace door has them.

Trane, American Standard, Carrier, Bryant, Lennox, Rheem and York furnace codes

Of the other brands, only Trane and Bryant have owner pages we could read, and neither publishes a code table; the table says what each brand's own page gives and where the legend lives.

We list codes only from manufacturer manuals or support pages. Third-party code lists are not reprinted here.

• Where the legend is on every brand: a label inside the blower compartment door, usually next to the control board's light, and the installation manual for the model number on the rating plate.
• Same family, same codes: Goodman and Amana share boards per their shared service manuals. Ask the company whether your brand shares a board with another; the technician will know.
• What to give the company: brand, model number from the rating plate, the color and count, and whether a reset cleared it.

What the repair costs once the code is read

Reading the code is a $75 to $150 an hour diagnostic visit in HomeGuide's figures, often applied to the repair, and the parts behind the common codes sit at the low end of furnace repair:

• Ignition failure or lockout: ignitor $100 to $250 (HomeGuide), $150 to $500 (HomeAdvisor); gas valve $200 to $800 (HomeGuide).
• Flame lost or weak flame signal: flame sensor cleaned or replaced, $80 to $250 (HomeGuide).
• Limit or overheating codes: limit switch $100 to $375 (HomeGuide); a filter if that was the cause. Repeated limit trips are how a heat exchanger gets damaged (Carrier).
• Pressure switch codes: often a blocked vent or drain; an inducer motor runs $400 to $1,100 (HomeGuide), $200 to $1,500 (HomeAdvisor).
• Rollout: the cause is usually in the burners or venting; parts vary. Not a part to reset and forget.
• Control board faults: $300 to $650 (HomeGuide), $200 to $600 (HomeAdvisor).
• Full part-by-part prices are on furnace repair; a furnace that cycles on a limit code is covered on furnace short cycling.

Furnace error codes: what to ask on the call

• What is the diagnostic fee, and is it applied to the repair? $75 to $150 an hour (HomeGuide).
• Do you service this brand? Say the model number.
• What did the code mean, and what did you find? Ask for the stored fault history on newer boards.
• Is the heat exchanger checked on an overheating code?
• License number and proof of insurance. Ask for the company's license number and proof of insurance yourself; the HVAC license table shows who licenses HVAC work by state.

Related: furnace blowing cold air, furnace tune-up, how long a furnace lasts and HVAC repair. Calls go to an independent heating and cooling company that serves your area and takes this kind of job; hours vary. How calls work.