High
b29 on Johnson Starley C16u

Your boiler has stopped working because the internal fan that clears away waste gases is spinning at the wrong speed.

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

Combustion air fan speed out of range (blocking mode)

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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Related fault codes

b28View →b30View →

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