F.01 — Return temperature sensor interruption

What does F.01 mean?

The boiler has detected an interruption in the return temperature sensor circuit. This prevents the boiler from accurately measuring the temperature of the water returning to it.

• Return NTC sensor plug is disconnected or loose.
• Multiple plug on the PCB is not correctly plugged in.
• Interruption or damage in the cable harness connected to the sensor.
• Return NTC sensor itself is defective.

Click steps to track your progress.

1. 1

   Visually check that all visible plugs for sensors and the main PCB are securely connected.

2. 2

   Press the fault clearance key on the boiler to reset it.

3. 3

   If the fault persists after resetting, contact Vaillant Service Solutions for diagnosis and repair.