Short answer: check the thermostat setting and batteries, check the breaker and any furnace power switch, and check that the gas valve is open. If all of that checks out and the furnace still won't run, it's a real repair — see the cost breakdown on our furnace repair page.
Checklist before you call
- Thermostat. Confirm it's set to "heat," the target temperature is above room temperature, and the batteries aren't dead (a blank display is a giveaway).
- Power. Furnaces typically have their own light-switch-style power switch near the unit, separate from the breaker panel — check both.
- Gas valve. Confirm the gas supply valve to the furnace is fully open (handle parallel to the pipe = open).
- Air filter. A severely clogged filter can trip a safety switch that shuts the whole system down as a protective measure.
- Pilot light or ignition sequence. Older systems have a visible pilot light; newer systems use an electronic igniter that will attempt to light a few times before locking out — if it's cycling and failing to light, that's an igniter or flame sensor issue.
If it's still not working
Most no-heat calls in this region come down to a failed igniter, a dirty flame sensor, or a tripped limit switch — see our full furnace repair cost guide for pricing by part. If you smell gas at any point, stop troubleshooting, leave the house, and call your gas utility's emergency line before calling anyone else.
Page last reviewed 2026-09-13.