High
F.21 on Vaillant Combi Compact 242EB

Your boiler has failed to ignite or stay lit, meaning it cannot provide heating or hot water until the ignition system is fixed.

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

The pilot flame has failed.

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

F.28View →F.29View →

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