Viessmann Indoor Room Temperature Sensor Out of Range

Indoor unit shows F1; unit may run with poor temperature control

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.

Possible Causes

Aging or drifted NTC sensor, Sensor relocated away from airflow, Poor contact between sensor and mounting point, Faulty indoor PCB ADC circuit

Safety: Turn off power before accessing the sensor.

Check sensor location: Ensure the room sensor is in the return air stream, not touching hot components or outside air leaks.
Replace sensor: If room temperature readings on the display are clearly inaccurate, replace the sensor with a Viessmann-compatible NTC.
PCB check: If a new sensor does not correct the issue, the indoor PCB may be misreading the sensor and require replacement.

Medium 3/5

Indoor Room Temperature Sensor (NTC)

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