High
F.12 on Vaillant Combi Compact 242EB

Your boiler has detected an internal blockage that is preventing water from circulating properly, causing it to stop its heating functions to protect itself.

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

A blockage in the appliance is affecting the system’s pressure.

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.20View →F.22View →F.24View →

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