F.85 — Fault: Flow and return temperature sensors incorrectly fitted

What does F.85 mean?

The boiler has detected that the flow and return temperature sensors are incorrectly fitted, possibly to the same pipe or the wrong pipes. This prevents accurate temperature measurement.

• Flow and/or return temperature sensors have been fitted to the same pipe.
• Flow and/or return temperature sensors have been fitted to the wrong pipes.
• Incorrect installation during maintenance or setup.

Click steps to track your progress.

1. 1

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

2. 2

   If accessible, visually check the installation of both the flow and return temperature sensors.

3. 3

   If the fault persists, contact Vaillant Service Solutions for professional inspection and correction.