Heating & Cooling Combined Unit: Why won’t my furnace burners won’t stay lit?
When your furnace burners ignite then shut off after several seconds, the flame sensor is likely dirty or it needs replacing. The flame sensor detects burner flames and shuts off gas going to the burners if it doesn’t detect burner flames.
You can shut off power to the furnace and clean the flame sensor using steel wool. Wipe the sensor with a cloth and reinstall it. Test the furnace to see if the flames keep burning. If not, then you’ll likely need to replace the flame sensor.
Less frequent causes of the furnace flame only igniting for a few seconds are damaged burners, lack of air flow and a bad high-temperature limit switch.
If you’re not able to determine why your furnace flames won’t stay lit, have a service technician diagnose and repair the furnace.
THESE REPAIRS MAY HELP SOLVE YOUR HEATING & COOLING COMBINED UNIT PROBLEM
Clean the furnace burner flame sensor
When the furnace burner ignites and only stays on for a few seconds, the flame sensor may be dirty. You can shut off power to the furnace and clean the flame sensor to troubleshoot the problem. You’ll typically find the flame sensor on the front burner box panel but the sensor can be located on the top or bottom of the burner housing as well. Remove the burner access panel and disconnect the flame sensor wire. Remove the flame sensor and clean it with steel wool. Wipe residue off the flame sensor and reinstall it. Reassemble the furnace and test burner operation. If burners stay lit, then cleaning the flame sensor fixed the burner problem. If flames still go out after a few seconds, then you may need to replace the flame sensor.
Clean the furnace burner flame sensor
Replace the furnace flame sensor
When the furnace burners only stay lit for a few seconds, a faulty flame sensor may be causing the failure. You can try cleaning the flame sensor to fix the problem. If flames don’t stay lit after cleaning the flame sensor, you’ll likely need to replace it.
Shut off electrical power for the furnace and remove the burner access cover. Disconnect the flame sensor wire and remove the flame sensor mounting screw. Pull the flame sensor out and replace it. Reassemble the furnace and restore electrical power.
Furnace flame sensor
How to replace the furnace flame sensor
Learn how to replace the flame sensor in your gas furnace when it doesn't detect the flame and the burners only light for a few seconds.
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