How to Fix / Troubleshooting

Safety: Turn off power and gas. Combustion components can be sharp and hot; allow cooling.

Inspect air intake: Check the combustion air intake pipe and terminal for obstructions such as leaves, insects, or snow. Clear any blockages.
Check fan operation: With the cover removed, briefly power the unit and observe whether the fan starts and runs smoothly. Turn power off again before touching the fan.
Inspect fan wiring: Ensure the fan connector is fully seated on the control board and that wires are not damaged.
Clean fan wheel: If accessible, clean dust and debris from the fan wheel and housing to reduce drag.
Replace fan if faulty: If the fan does not start, makes grinding noises, or the speed feedback is incorrect, replace the combustion fan assembly with a Buderus-approved part.
Reassemble and test: Refit covers, restore gas and power, and run the heater to confirm that H41 does not return.

Heater shows H41; performance may be reduced or unit may shut down intermittently.

Possible Causes