Furnace Reset Button: Where It Is and When to Use It
Ben Amina
Aire One East Heating & Cooling, 1910 Dundas St E #117, Whitby
The furnace reset button is the first thing many homeowners look for when the heat stops, but most modern gas furnaces do not have one big button to press. Instead, a gas furnace is reset by turning its power off and on, which clears a safety lockout. Oil furnaces are different: they have a red reset button on the oil burner, and pressing it more than once can be dangerous. Some furnaces also have small manual reset switches that trip only when something is seriously wrong. This guide explains where the furnace reset button is on each type of furnace, how to reset your furnace safely, why it keeps needing a reset, and when to stop and call a licensed technician in Durham Region.
- Most gas furnaces have no single furnace reset button. You reset them by turning off the furnace switch or breaker for about 30 seconds.
- Oil furnaces have a red reset button on the burner. Press it once only. Pressing it again and again can flood the burner with oil.
- Some furnaces have manual reset rollout or limit switches. If one trips, something is wrong and a technician should find out why.
- Before resetting, check the thermostat, the filter, the furnace door, and the vent pipes outside.
- If the furnace needs a reset more than once, stop and call for service.
Short answer: On most gas furnaces the furnace reset button is really the power switch: turn off the furnace service switch or breaker, wait about 30 seconds, and turn it back on. On an oil furnace, press the red burner reset button once only. If the furnace locks out again, call a licensed technician.
Aire One East provides 24/7 furnace repair across Durham Region. Call 905-576-7600.
Where is the furnace reset button?
Where you find the furnace reset button depends on the type of furnace you have:
- Gas furnaces: most have no dedicated reset button. The reset is the furnace service switch, a light switch on or near the furnace, or the furnace breaker in your electrical panel. Turning the power off for about 30 seconds clears the lockout on the control board.
- Oil furnaces: the reset button is a red button on the burner control, usually on the side of the oil burner near the front of the furnace.
- Manual reset safety switches: some furnaces have a small button on a flame rollout switch near the burners, or on a high limit switch. These are not everyday reset buttons. They trip when flames or heat go where they should not.
- Older blower motors: some older blower motors have a small thermal reset button on the motor itself.
If you are not sure which type you have, look at the label inside the furnace door or check the model number. A furnace with white plastic vent pipes on the side of the house is almost always a high efficiency gas furnace.
Check these before you press any furnace reset button
- Thermostat: make sure it is set to heat and a few degrees above room temperature, and replace the batteries if the screen is blank. Our thermostat not working guide has more checks.
- Furnace filter: a clogged filter can make the furnace overheat and shut down. Replace it if it is dirty.
- Furnace door: a safety switch keeps the furnace off if the blower door is not fully closed.
- Power: check that the furnace service switch is on and the breaker has not tripped.
- Gas supply: check that other gas appliances work and the gas valve to the furnace is open.
- Vent pipes: after a storm, check that snow or ice is not blocking the pipes outside. See our furnace vent blocked by snow guide.
How to reset a gas furnace without a reset button
- Turn the thermostat down or to off.
- Turn off the furnace service switch or the furnace breaker.
- Wait about 30 seconds. This lets the control board clear its lockout.
- Turn the power back on and set the thermostat to heat, a few degrees above room temperature.
- Listen and watch. You should hear the inducer fan, then the igniter, then the burners, and after a short delay the blower.
If the furnace runs normally, keep an eye on it for the rest of the day. If the status light on the control board starts flashing again, write down the pattern. Our furnace blinking light guide explains what the common codes mean.
How to use the furnace reset button on an oil furnace
On an oil furnace, the furnace reset button is the red button on the burner control. If the burner fails to light, the control locks out and the button pops up. Press it once and hold it for a second or two. If the burner lights and runs, the problem may have been temporary.
If it does not light, do not press the furnace reset button again. Each failed attempt can leave unburned oil in the combustion chamber, and repeated resets can lead to a puff back or a fire when the oil finally ignites. Check that the tank has oil and the oil valve is open, then call a technician. Many rural homes around Uxbridge and Port Perry still heat with oil, and we see this mistake every winter.
Why your furnace keeps needing a reset
A furnace that needs a reset over and over is telling you something. The most common causes are:
- A dirty flame sensor that cannot confirm the flame, so the furnace shuts off a few seconds after lighting. See our furnace flame sensor guide.
- A weak or cracked igniter that fails to light the burners. See our furnace igniter guide.
- Overheating from a dirty filter, closed vents, or a failing blower, which trips the high limit switch.
- A blocked vent or condensate line that trips the pressure switch.
- A tripped rollout switch, which can point to a blocked heat exchanger or a cracked heat exchanger. Never reset a rollout switch more than once. Read our cracked heat exchanger guide to understand why.
When to stop and call a technician
Stop using the furnace reset button and call a licensed technician if the furnace locks out again after one reset, if a manual rollout or limit switch has tripped, if you smell gas or burning, if you see scorch marks near the burners, or if your carbon monoxide alarm sounds. A reset clears the symptom, not the cause, and repeated resets can hide a safety problem.
Our team provides furnace repairs 24/7 across Durham Region, and our maintenance and protection plans include a yearly cleaning of the flame sensor, igniter check, and safety control test, which prevents most lockouts before winter. If your furnace keeps failing and is getting older, our repair or replace guide can help you decide what to do next.
Key terms in this article
- Lockout: a safety state where the furnace stops trying to start after repeated failures
- Service switch: a light style switch near the furnace that turns its power on and off
- Flame rollout switch: a safety switch that trips if flames roll out of the burner area
- High limit switch: a safety switch that shuts off the burners if the furnace overheats
- Puff back: a small explosion in an oil burner caused by unburned oil igniting
- Control board: the electronic board that runs the furnace and flashes fault codes
Frequently asked questions
| Your furnace reset button questions, answered |
|---|
| Where is the reset button on a gas furnace? Most gas furnaces do not have a single furnace reset button. You reset them by turning off the furnace service switch or breaker for about 30 seconds, then turning it back on, which clears the lockout on the control board. |
| How many times can I press the furnace reset button? Once. On an oil furnace, repeated presses can flood the burner with oil and cause a puff back. On a gas furnace, if it locks out again after one reset, call a technician to find the cause. |
| Why does my furnace keep needing to be reset? Common causes are a dirty flame sensor, a weak igniter, overheating from a dirty filter, a blocked vent or condensate line, or a tripped rollout or limit switch. A technician can find which one. |
| Is it safe to reset my furnace? Resetting once after checking the thermostat, filter, power, and vents is safe. Do not keep resetting, never bypass a safety switch, and leave right away and call for help if you smell gas or your CO alarm sounds. |
| What does the red button on my furnace do? On an oil furnace, the red button resets the burner control after a failed ignition. On some gas furnaces, a small red button on a rollout or limit switch resets a safety switch that tripped for a reason. Have a technician check it. |
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References and further reading
