F.01
Return temperature sensor fault
The return temperature sensor circuit is interrupted or the sensor signal is unavailable.
What this code means
The return temperature sensor circuit is interrupted or the sensor signal is unavailable.
Possible causes
- Return NTC sensor disconnected or defective
- Loose PCB connector
- Break in cable harness
Common symptoms
- F.01 displayed
- Boiler may stop or control temperatures incorrectly
Checks to make
- Arrange qualified diagnosis of the return-temperature sensor and wiring
Safety
- Do not remove the boiler casing or work on gas, combustion, flue or internal electrical components unless appropriately qualified. If gas is suspected, follow the national gas-emergency procedure.
Model notes
Vaillant notes that not every fault code is visible on every product model.