F19
Viessmann
Sensor plausibility / multiple sensor disagreement
Sensor plausibility error, temperature readings inconsistent or out of range
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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
One or more NTC sensors out of calibration, Poor sensor contact on pipes, Incorrect sensor placement after service, Faulty control board analog circuitry
How to Fix / Troubleshooting
Safety: Turn off power and allow the system to cool.
- Compare sensors: Touch the flow and return pipes near their sensors; they should feel consistent with displayed temperatures. Large discrepancies suggest a sensor issue.
- Check sensor mounting: Ensure all clip-on sensors are firmly attached and insulated from ambient air.
- Inspect wiring harness: Look for damaged or swapped sensor connectors on the control board.
- Reset: After correcting any obvious issues, reset the boiler and monitor operation.
- Professional diagnostics: A technician can measure each sensor and compare to Viessmann charts to identify the faulty component.
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Repair Difficulty
Hard
4/5
Required Part
Temperature Sensor Harness
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