High
F.23 on Vaillant ecoTEC plus Aquaplus

Your boiler has detected that water is not circulating properly, meaning it cannot safely heat the system.

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

Dry fire protection (difference between flow and return NTC's too large) | No water in appliance, pump cable defective, pump blocked or defective, pump output too low

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.22View →F.24View →

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