High
F.83 on Vaillant ecoFIT Pure 418

Your boiler is struggling to detect the expected temperature difference between the water leaving and returning to the system, causing it to shut down to prevent damage.

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

Fault: Flow and/or return temperature sensor temperature change too small

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.73View →

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