When the heat goes out, comfort drops fast—but not every problem needs a repair call. Try these simple checks first to see if you can get your system running again safely.
1. Confirm thermostat settings
Make sure the thermostat is set to Heat, not Cool or Off.
Raise the set temperature 3–5 degrees above room temperature.
Replace thermostat batteries if the screen is dim, blank, or unresponsive.
2. Check the power and breaker
Look at your electrical panel for a tripped breaker and reset it once if needed.
Verify the furnace or air handler switch (often looks like a light switch nearby) is in the On position.
If power trips again, stop and call a professional—there may be an electrical fault.
3. Verify the furnace door and safety switches
Many furnaces will not run if the front access panel is not fully closed.
Open the panel, check for anything obvious out of place, then close it firmly until it clicks.
Wait a few minutes and see if the system starts up.
4. Replace or clean the air filter
A clogged filter can make the system overheat and shut down for safety.
Locate the filter, slide it out, and check: if it’s gray, dusty, or hard to see light through, replace it.
Use the same size and orientation (airflow arrow pointing toward the furnace).
5. Check supply and return vents
Walk through the home and confirm vents are open and not blocked by furniture, curtains, or rugs.
Keep return grilles clear so air can flow back to the system.
Avoid closing too many vents in unused rooms, which can stress the system.
6. Look at the pilot light or ignition
(For older gas furnaces with a standing pilot)
If the pilot light is out, follow the manufacturer’s lighting instructions on the unit label.
If the flame will not stay lit or you smell gas, stop immediately and call a pro or your gas company.
(For modern furnaces with electronic ignition)
These use spark or hot-surface igniters; if you hear repeated clicking with no start, it likely needs professional service.
7. Make sure the gas or fuel is on
Confirm the gas shutoff valve near the furnace is parallel to the pipe (On position).
If you use propane or oil, check the tank gauge to ensure you’re not out of fuel.
If you ever smell strong gas, leave the building and contact emergency services—do not keep troubleshooting.
8. Inspect the outdoor unit (for heat pumps)
If you have a heat pump, check the outdoor unit for snow, leaves, or debris blocking airflow.
Gently clear away obstructions and make sure the unit is not buried or iced over.
If there is heavy ice buildup, turn the system off and call a professional.
9. Check for error codes or indicator lights
Many furnaces have a small viewing window with an LED that blinks in a pattern.
Note the blink pattern and keep it handy for the technician—it helps pinpoint the problem.
Some smart thermostats also show specific error messages or lockouts.
10. Give the system a “soft reset”
Turn the thermostat to Off and the system switch at the furnace to Off.
Wait 5–10 minutes, then turn the furnace switch On and reset the thermostat to Heat.
Listen for the sequence: blower, ignition, and warm air from vents. If it still fails, it’s time to call for service.
When to stop and call a professional
You smell gas, burning, or strong electrical odors.
The breaker keeps tripping or the furnace shuts down repeatedly.
You see visible damage, scorch marks, or loose wiring.
A quick visual and basic check often brings a non-working heater back online, but if these steps don’t help—or anything seems unsafe—shutting it down and calling a licensed technician is the safest move.
