F.75 — Fault: No pressure change detection when starting pump

What does F.75 mean?

The boiler has failed to detect a change in water pressure when the pump starts, indicating a circulation problem or a faulty sensor/pump. The boiler may be unable to circulate water effectively.

• Water pressure sensor and/or circulation pump is defective.
• Air trapped in the heating installation.
• Water pressure in the boiler is too low.
• Adjustable bypass is incorrect, or an external expansion vessel connection issue.

Click steps to track your progress.

1. 1

   Check the boiler pressure and top up the water if it is below 1.0 bar.

2. 2

   Bleed air from your radiators and heating system.

3. 3

   Press the fault clearance key on the boiler to reset it. If the fault persists, contact Vaillant Service Solutions.