F86 Medium

Heatline F86 Fault Code

The Heatline F86 fault code means: your boiler has detected a problem with the safety connection for your underfloor heating system, which usually means a sensor is loose or has shut the system down to prevent floor damage.. It appears on 8 Heatline models in our database.

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.

Technical description: Underfloor heating contact fault: Floor heating contact open / Sensor disconnected or defective
Typical repair cost £90-180 (including labour)

Engineer required

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

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Heatline models that show the F86 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Heatline F86 fault code information on this page is sourced and cross-checked against the official Heatline service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026