Medium
F.86 on Vaillant Home System

Your boiler has detected an issue with the electrical connection to your underfloor heating system, preventing that part of your home from warming up properly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Underfloor heating contact fault

From this model's manual
Verified against the Vaillant Home System installation & service manual, page 35.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.83View →F.84View →F.85View →

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