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Furnace Reset Button and Blinking Light Codes: What You Can and Can't Do

Updated November 2, 2026 · General information, not HVAC or gas-fitting advice

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Gas smell, hissing, or a carbon monoxide alarm sounding? Stop reading and get out. Do not turn anything on or off and do not look for the cause. From outside, call 911 and your gas utility. Go back in only when responders say it is safe. Gas smell steps · CO alarm steps

The short answer: Fault codes are specific to the furnace maker. The legend is on the inside of the access door (ServiceMag), so read your own label and manual. We found no sourced general reset procedure, so we give none. A homeowner can reset a tripped breaker once. Anything involving burners, gas or safety switches is for a licensed technician.

Safety first. Gas, burners, venting and wiring are jobs for a licensed HVAC professional. This page covers only checks a homeowner can do without opening the furnace or touching gas parts.

Blinking light codes

ServiceMag says the board's LED fault code is read from the legend inside the access door, and lists reading it as technician work. We opened no manufacturer manual, so we do not list codes. A generic code table could be wrong for your furnace.

What helps: write down the pattern (for example, "two flashes, pause") and tell the technician. Our suggestion; the pages we opened do not say this.

Reset buttons

Breaker. Erie Institute of Technology's guide includes trying the circuit breaker. If it trips again, stop and call a licensed professional (our suggestion).
Gas valve pilot or reset button. On a standing-pilot furnace, the button is used when relighting the pilot. Budget Heating says releasing the reset too quickly is unsafe because the safety device needs time to heat. See pilot light out.
Safety switches. ServiceMag warns never to jumper a limit switch, because bypassing it can ruin the heat exchanger.

Do not

Do not keep pressing reset over and over. A furnace that needs repeated resetting has a problem (our suggestion).
Do not open the burner area or bypass any safety device.
If you smell gas, leave and call.

Not sure what is wrong?

Answer a few questions about what the furnace is doing. The checker starts with a safety screen, then points you to the likely causes and next steps.

Open the furnace checker

Checks did not fix it?

Gas, burner, ignition and venting problems are for a licensed HVAC technician. Our guide covers which signs mean call now.

When to call an HVAC technician Find a licensed HVAC pro near you

Common questions

Where is the furnace error code legend?

ServiceMag says the legend for the board's LED fault codes is on the inside of the access door.

Can I bypass a safety switch to get heat?

No. ServiceMag says bypassing a limit switch can ruin the heat exchanger and never to jumper one.

Related guides

When to call an HVAC technician

Sources