F09
Vaillant
Valve Home Position Not Detected
F09 error and the unit cannot enter service mode after regeneration
Advertisements
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.
Advertisements
Possible Causes
Misaligned rotor in control head, Damaged cam or position disk, Faulty home position switch, Wiring fault between switch and PCB
How to Fix / Troubleshooting
Safety: Disconnect power and close the inlet valve before opening the control head.
Procedure:
- Visual inspection: Remove the control head cover and locate the cam or disk that actuates the home position switch. Check for cracks, missing tabs, or misalignment.
- Check microswitch: Manually operate the home position switch and listen for a clear click. Use a multimeter (if competent) to verify continuity when pressed. Replace the switch if it fails.
- Realign rotor: Follow the service manual to set the rotor to the correct home position (usually a marked alignment between the rotor and housing). Tighten any retaining screws.
- Inspect wiring: Ensure the switch wiring harness is intact and firmly connected to the PCB. Repair or replace damaged cables.
- Test cycle: Restore power, clear the F09 code, and run a manual regeneration. Confirm that the unit returns to service without re‑triggering the error.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Valve Position Switch / Cam Assembly
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements