E03 High

Heatline E03 Fault Code

The Heatline E03 fault code means: your boiler has detected an issue with the sensor that monitors the temperature of the water used for your heating, causing the system to stop working for safety.. It appears on 2 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: High limit thermostat 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 E03 fault code

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

Source

Heatline E03 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 31 August 2026