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Vaillant aroTHERM fault F.103

Fault: spare part ident

Heat pump

What it means

Incorrect control PCB installed on the outdoor unit.

Likely causes

  1. Incorrect control PCB installed on the outdoor unit
  2. Installation and type of heating installation
  3. User behaviour
  4. Seasonal influences
  5. Tolerances and components
  6. External consumers/generators not accounted for

Where to start

  1. Check PCB part identification against outdoor unit requirements
  2. Use the sensor/actuator test to verify the EEV moves to the limit stop
  3. Use the sensor/actuator test to verify the 4-port diverter valve produces an audible switching sound when actuated

The full answer, free

  • 22 more checks in order
  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 34), right under the answer
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Safety: Isolate the outdoor unit and any backup heater, and give the inverter capacitors time to discharge before you open the electrics. Anything on the refrigerant circuit needs F-gas certification.

From the Vaillant manual for the aroTHERM. Check the model on the data plate before you order parts.

Other Vaillant aroTHERM fault codes