F85 High

Heatline F85 Fault Code

The Heatline F85 fault code means: your boiler's temperature sensors are reporting conflicting information because they are detecting heat from the same spot, causing the system to stop heating for safety.. It appears on 8 Heatline models in our database.

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: Flow and return heating sensors fault: Flow and return heating temperature sensor connected to same tube
Typical repair cost £120-220 (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 F85 fault code

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

Source

Heatline F85 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 27 April 2026