F5 High

Heatline F5 Fault Code

The Heatline F5 fault code means: your boiler has detected that a safety sensor measuring exhaust gas temperatures is broken or malfunctioning, causing the system to shut down for safety.. It appears on 10 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: Combustion product (flue) temperature probe damage
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 F5 fault code

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

Source

Heatline F5 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