How much does it cost to fix boiler error code Phase reversed neon (behind the knob) lighting?

Typical repair cost for the boiler Phase reversed neon (behind the knob) lighting fault is £80-140 including labour.

Phase reversed neon (behind the knob) lighting High

Boiler Fault Code Phase reversed neon (behind the knob) lighting

Also written as PHASEREVERSEDNEONBEHINDTHEKNOBLIGHTING — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 7 July 2026

Fault code Phase reversed neon (behind the knob) lighting appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected that the incoming electrical wires are connected the wrong way around, preventing it from safely starting the main burner. (As reported on Malvern TenTwenty)

Pick your boiler brand for the Phase reversed neon (behind the knob) lighting fix

Malvern Phase reversed neon (behind the knob) lighting 1 model

Source

Information for the Phase reversed neon (behind the knob) lighting fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026