Boiler reports a flue gas sensor or air pressure related fault; may not ignite.
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: Turn off power and gas. Flue and combustion air issues can lead to dangerous operation; if unsure, call a professional.
User‑level checks:
- Visually inspect the outside flue terminal for obstructions (ice, debris, nests) and clear if safe.
- Check that the condensate pipe is not frozen or blocked; thaw and clear as needed.
Technician tasks (for reference): A professional will test the air pressure switch, inspect and clear the flue, check fan operation, and verify condensate trap and hoses.
Repair Difficulty
Required Part
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