Furnace Not Turning On? Troubleshooting Steps Before You Call
Nothing gets urgent faster than a furnace that quits on a freezing night. Run through this before you call, then call us if it's on the second list.
Check these yourself first
- Thermostat: set to HEAT, temperature above room temp, batteries fresh.
- Breaker: furnaces have a dedicated circuit — reset it once.
- Furnace switch: that light-switch on the unit gets flipped by accident constantly.
- Filter: a clogged filter trips the high-limit and shuts the burners down.
- Gas valve: confirm the shutoff at the furnace is open.
- Blower door panel: if it isn't seated, the safety interlock keeps the furnace off.
- Condensate drain: high-efficiency furnaces shut off on a full or clogged drain.
Now leave it to a technician
Failed hot-surface igniter
The most common no-heat part. You'll hear the inducer spin, then a click, then nothing. Igniters are fragile and typically last five to seven years.
Dirty flame sensor
Furnace lights for a few seconds then shuts off, repeating three or four times before locking out. The sensor is carbon-coated and can't confirm flame. Cleaning is a fast fix.
Bad pressure switch or blocked flue
A safety device confirming the exhaust is clear. Blocked flues are genuinely dangerous — birds' nests, ice and collapsed venting all cause it.
Cracked heat exchanger
This one matters most. A cracked exchanger can leak carbon monoxide into your home. If our combustion analysis and inspection confirm a crack, the furnace must be shut down. See furnace replacement.
Need help now? We run 24/7 emergency heating repair with no after-hours surcharge.
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