A6
Viessmann
Indoor Fan Motor Fault
Indoor unit attempts to start but fan does not run; A6 error displayed
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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.
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Possible Causes
Failed indoor DC fan motor, Faulty fan motor driver circuit on PCB, Jammed blower wheel, Loose or damaged fan motor wiring harness
How to Fix / Troubleshooting
Safety: Turn off power at the breaker. The fan blades can be sharp; wear gloves.
- Check for obstructions: Remove the front cover and carefully spin the blower wheel by hand. It should rotate freely without scraping. Remove any foreign objects.
- Inspect wiring: Verify the fan motor connector is fully seated on the indoor PCB and that wires are not pinched or burnt.
- Test motor (basic): With power restored briefly, command the fan to run (fan-only mode). If the motor hums but does not turn, or does nothing at all, it is likely defective.
- Replace fan motor: If the blower is free and wiring is intact but the motor does not run, replace the indoor fan motor assembly with a Viessmann-compatible unit.
If a new motor still triggers A6, the indoor PCB fan driver circuit is likely faulty and the board should be replaced.
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Repair Difficulty
Hard
4/5
Required Part
Indoor DC Fan Motor
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