DIY reset guide
How to reset a furnace
By the HeatAndAirCost editors · Last updated September 3, 2026 · How we research prices
Short answer
To reset a furnace, flip the furnace power switch off, wait 30 seconds, and turn it back on. If that does not restore heat, press the reset button once, then wait a minute for the furnace to try to start[1]. Reset a furnace only once. If it trips out again, stop and call a technician rather than resetting repeatedly.
Stop and leave if you smell gas
A rotten-egg or sulfur smell means a gas leak. Do not touch any switch, do not use your phone indoors, and do not attempt a reset. Leave the house, then call your gas utility and 911 from outside. Do not go back in until they clear it. The same applies if a carbon monoxide alarm is sounding.
The reset steps, in order
Every step here stays at the switch, breaker, filter, and thermostat level. None of it involves opening the sealed combustion chamber or bypassing a safety switch.
- Set the thermostat correctly. Switch it to HEAT and raise the target at least 5 degrees above the current room temperature. Replace the batteries while you are there. A thermostat in FAN or OFF never calls for heat.
- Cycle the furnace power switch. The switch looks like a normal wall light switch, usually mounted near the unit or at the top of the basement stairs. Turn it off, wait 30 seconds, and turn it back on. This is the gentlest reset there is.
- Reset the breaker if it tripped. At the electrical panel, find the breaker labeled FURNACE or HVAC. If it is tripped, push it fully to OFF, then back to ON. Do not repeatedly reset a breaker that keeps tripping.
- Replace a dirty filter. A packed filter can overheat the furnace and trip its high-limit switch. Swap in a clean filter and the unit may restart on its own.
- Press the reset button once. Many furnaces have a red or yellow reset button on the blower or burner housing. Press it a single time and wait about a minute. If it trips again quickly, do not keep pressing it.
- Close the access panel fully. A door safety switch cuts power when the panel is ajar. Seat it firmly until it clicks, then try the thermostat again.
When a reset will not fix it
If the furnace trips out a second time, a reset is no longer the answer. The most common underlying faults are a dirty flame sensor, a worn igniter, a blocked pressure switch, or a control board that has failed[1]. Those need a technician to diagnose safely. Our furnace not turning on guide walks through each one, and furnace blowing cold air covers the case where the blower runs but no heat comes out.
If a visit is next
A diagnostic call runs $75 to $200[2]; see the full breakdown on our HVAC service call cost page. If the furnace fails overnight in freezing weather, emergency HVAC cost explains the after-hours surcharge.
People also ask
Furnace reset FAQs
How do I reset my furnace?
Turn the furnace power switch off, wait 30 seconds, and turn it back on. If that does not clear the fault, find the reset button, usually a red or yellow button on the blower or burner housing, and press it once. Give the furnace a minute to attempt a start. Reset a furnace once, not repeatedly.
How do I reset a furnace that won't turn on?
Start at the thermostat: set it to HEAT, above room temperature, and replace the batteries. Then cycle the furnace power switch off and on, and check the breaker. If the furnace has a reset button, press it a single time. If it still will not start, or the button trips again, the fault is deeper than a reset can fix and needs a technician.
How do I force my furnace to start?
There is no safe way to force a furnace past its own safety controls, and you should not try. What you can do is clear the common blocks: correct thermostat settings and fresh batteries, the power switch on, the breaker set, a clean filter, and the access panel fully closed so the door switch engages. Those are the only starts worth forcing.
Why does my furnace keep needing a reset?
A furnace that trips out repeatedly is telling you something is wrong. Common causes are a dirty flame sensor, a clogged filter overheating the unit, or a failing igniter or pressure switch. Resetting again and again masks the fault and can damage the equipment. After the second trip, book a diagnostic visit instead of resetting a third time.
Reset didn't hold?
Get a fair repair quote
If the furnace keeps tripping out, a licensed technician can diagnose the root cause. Know the fair price before you agree to any work.