Furnace runs but carbon monoxide detector alarms when it operates
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: This is an emergency. Turn off the furnace and all fuel-burning appliances immediately. Open windows and leave the building until it is safe.
Actions:
- Do not operate the furnace: Leave it off until inspected by a licensed HVAC technician.
- Check CO detector: Verify the detector is not expired and is installed according to manufacturer instructions.
A professional must inspect the heat exchanger, venting, and combustion air supply. Do not attempt to repair a suspected CO issue yourself.
Repair Difficulty
Required Part
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