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2FMEDIUM

Outdoor Temperature Sensor Fault (Viessmann)

Viessmann boiler outdoor temperature sensor has failed or is providing an incorrect reading.

What This Error Code Means

The outdoor temperature sensor circuit is open, shorted, or reading outside the valid range.

Common Causes

  • Sensor wiring damaged or disconnected
  • Outdoor sensor failed
  • Corrosion at sensor connections
  • Sensor location exposed to direct sun
  • Water ingress in sensor housing

Affected Brands

Viessmann

How ROMA Heating Fixes This

  • Check sensor wiring for damage
  • Measure sensor resistance and compare to temperature
  • Clean sensor connections
  • Replace outdoor temperature sensor
  • Verify weather-dependent control operation

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Seeing Error Code 2F?

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