or "Fan speed out of range" . The boiler’s printed circuit board (PCB) has detected that the combustion fan is not spinning at the correct speed required for safe operation.
If your Vaillant boiler has locked out and is displaying the , it usually indicates an issue with the electronics—specifically concerning the gas valve or the main Printed Circuit Board (PCB). vaillant boiler f64 fault
In most cases, . Because the F64 fault involves internal electrical components and the central control system, it requires a professional diagnostic. or "Fan speed out of range"
Boilers are often located in kitchens or utility rooms where condensation or leaks can occur. If water has dripped onto the PCB or the gas valve wiring harness, it can cause short circuits, leading to a multitude of error codes, including F64. In most cases,