High
F.85 on Vaillant ecoFIT Pure 825

Your boiler has detected that the internal temperature sensors are mismatched or incorrectly fitted, preventing it from safely regulating heat.

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: Temperature sensors installed incorrectly

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.83View →

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