How to Reset Your Furnace Your Furnace Limit Switch Safely

If your furnace keeps shutting off, the limit switch is likely tripped—here’s how to reset furnace limit switch safely and restore heat fast. No technician needed, just a few simple steps you can follow right now.

Why the Furnace Limit Switch Trips

The limit switch is a tiny safety button that cuts power when the furnace overheats, protecting the blower motor and heat exchanger. When it trips, the furnace stops heating until you manually reset it. Many homeowners mistake this for a major breakdown and pay for a service call that could have been avoided.

Understanding that the switch is just a pop‑out button saves time, money, and frustration. A quick visual check tells you if it’s open or closed, and pushing it back in usually brings the heat back on.

Step‑by‑Step: How to Reset Your Furnace Limit Switch

Safety first—always cut power and gas before touching any furnace component.

1. Turn off power and gas
Flip the furnace breaker to off. Then locate the gas valve on the supply line and turn it to the off position. This prevents sparks or gas flow while you work.

2. Find the limit switch
Open the furnace access panel (usually a few screws or clips). Inside you’ll see a round or rectangular button with a small lever—often red or yellow—near the blower motor. That’s the limit switch. If unsure, consult the wiring diagram glued inside the panel.

3. Test the switch
If you have a multimeter, set it to continuity and place probes on the switch terminals. A reading means the switch is closed; no reading means it’s tripped. Without a meter, simply look at the lever: if it’s popped out or stuck, the switch is open.

4. Reset the switch
Gently push the lever back in or press the button until you hear a click. You should feel it snap into place. That’s the reset.

5. Restore power and test
Return the gas valve to on, flip the breaker back on, and set your thermostat to call for heat. The furnace should ignite within a minute and warm air should flow. If it shuts off again immediately, check for a dirty filter, blocked vent, or blower issue—these are common causes of repeated tripping.

Keep the Limit Switch From Tripping Again

After a successful reset, inspect the air filter and replace it if dirty. Ensure all vents and returns are unobstructed. Verify the blower motor runs smoothly and isn’t overheating. Regular maintenance prevents the limit switch from tripping repeatedly and keeps your home warm all season.