High
F.17 on Vaillant Atmomax

Your boiler has detected an electrical issue where the incoming power wires may be connected in the wrong order or there is an unstable voltage supply.

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

Check the polarity of your system.

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.26View →F.27View →F.68View →

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