Select a fault code

System pressure has dropped below the minimum. One of the most common Vaillant fault codes.

The boiler has attempted to ignite but failed after multiple attempts.

The boiler lit but the flame extinguished unexpectedly.

Fault detected in the gas valve wiring or gas valve actuation.

The gas valve is not closing properly, causing a safety lockout.

A fault has been detected in the main circuit board memory.

The water pressure sensor is sending an implausible signal.

Pressure sensor voltage is outside acceptable range.

No pressure change detected when the pump started — pump or pressure sensor fault.

Condensate pump has failed or condensate pipe is blocked.