What Does the Vaillant F29 Fault Code Mean? A Vaillant F.29 fault code means the boiler lit successfully, but the flame went out during normal operation and could not reignite after repeated attempts. Unlike an F.28 ignition lockout, F.29 signals unexpected mid-cycle flame loss. The top immediate field causes behind this lockout include: If a … Continue reading Vaillant F29 Fault Code