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HVAC
Why is my furnace not producing heat?
Furnace running but no heat? Here's how to diagnose it in 5 minutes and what to check before calling an HVAC tech.
Most common causes
- 01Dirty filter restricting airflow
- 02Pilot light out or igniter failed
- 03Thermostat set to fan-only instead of heat
- 04Tripped high-limit switch (overheated)
- 05Gas supply issue
- 06Cracked heat exchanger
What to do right now
1
Set thermostat to heat mode and 5 degrees above current temperature2
Check that the filter is clean3
Listen for the igniter clicking — if it clicks but doesn't light, the igniter may have failed4
Check that the gas supply valve to the furnace is in the open position (handle parallel to pipe)When to call a professional
Call immediately if: you smell gas (leave the home, call gas company first), the furnace short-cycles (turns on and off rapidly), or there's a yellow flame visible instead of blue.
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