How much does it cost to fix Heatline error code Flashing 90?

Typical repair cost for the Heatline Flashing 90 fault is £120-250 including labour.

Flashing 90 High

Heatline Flashing 90 Fault Code

Q: What does the Heatline Flashing 90 fault code mean?

Your boiler has detected that it is running too hot and has automatically switched itself off to prevent internal damage.

Also written as FLASHING90 — same fault.

The Heatline Flashing 90 fault code means: your boiler has detected that it is running too hot and has automatically switched itself off to prevent internal damage.. It appears on 2 Heatline models in our database.

Technical description: Overheat Thermostat

Typical repair cost £120-250 (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 Flashing 90 fault code

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

Source

Heatline Flashing 90 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