F.64 — Electronics/NTC fault

What does F.64 mean?

The boiler's electronics or an NTC (Negative Temperature Coefficient) sensor has developed a fault. This could affect temperature readings or overall boiler control.

• Supply or return NTC sensor is short-circuited.
• Main electronics board of the boiler is defective.

Click steps to track your progress.

1. 1

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

2. 2

   Visually inspect any accessible wiring to the flow and return NTC sensors for signs of damage.

3. 3

   If the fault persists, contact Vaillant Service Solutions, as this indicates an internal electronic fault.