Furnace locks out with A41; may indicate flue gas temperature too high
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. Overheated flue components can be extremely hot; allow time to cool.
- Check flue terminal: Inspect the outside flue terminal for obstructions. Remove any blockage and ensure proper clearances from walls, windows, and vents.
- Inspect condensate drain: A blocked condensate trap or hose can cause flue gas recirculation. Check the Bosch condensate trap for sludge and clean according to the manual. Ensure the drain line slopes correctly and is not frozen.
- Flue gas sensor: Locate the flue gas temperature sensor on the flue outlet. Check wiring and connector. If the sensor is cracked or discolored, replace it.
Do not attempt to adjust gas valve settings yourself. If A41 recurs, a qualified technician must check combustion, gas pressure, and heat exchanger condition.
Repair Difficulty
Required Part
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