F18
Viessmann
Configuration / Parameter Fault
F18 displayed, unit indicates sensor calibration or configuration error
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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
Incorrect parameter settings in installer menu, Wrong sensor type configured, Corrupted EEPROM on control board, Unauthorized changes to service settings
How to Fix / Troubleshooting
Safety: Only qualified personnel should change installer-level parameters. Incorrect settings can damage the appliance.
- Check parameter set: Access the installer menu using the Viessmann code and verify that the appliance type, gas type, and sensor configuration match the installed hardware.
- Restore defaults: If available, use the menu option to restore factory default parameters, then re-enter only the necessary commissioning values.
- Do not guess: If you are not trained on Viessmann controls, do not alter advanced parameters. Contact a Viessmann service partner.
- Board replacement: If parameters cannot be saved or F18 persists, the EEPROM or control board may be defective and require replacement.
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Repair Difficulty
Professional Required
5/5
Required Part
Main Control PCB
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