How much does it cost to fix Heatline error code F4?

Typical repair cost for the Heatline F4 fault is £100-180 including labour.

F4 Medium

Heatline F4 Fault Code

Q: What does the Heatline F4 fault code mean?

Your boiler is struggling to detect the temperature of the water being heated for your taps, which means it will likely stop providing hot water until the faulty sensor is replaced.

The Heatline F4 fault code means: your boiler is struggling to detect the temperature of the water being heated for your taps, which means it will likely stop providing hot water until the faulty sensor is replaced.. It appears on 10 Heatline models in our database.

Technical description: Domestic Hot Water (DHW) sensor fault

Typical repair cost £100-180 (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 F4 fault code

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

Source

Heatline F4 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