High
Neon L3 on Halstead Hero

Your boiler is struggling to clear exhaust fumes because it cannot confirm that the internal fan is moving air properly, preventing it from lighting safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Fan operation indicator / Air Pressure Switch check

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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