How much does it cost to fix Ideal error code L1?

Typical repair cost for the Ideal L1 fault is £120-£350 including labour.

L1 High

Ideal L1 Fault Code

Q: What does the Ideal L1 fault code mean?

Your boiler has switched itself off because the internal water temperature has become too hot, usually caused by a lack of water flow through the system.

The Ideal L1 fault code means: your boiler has switched itself off because the internal water temperature has become too hot, usually caused by a lack of water flow through the system.. It appears on 19 Ideal models in our database.

Technical description: Flow Temperature Overheat Lockout

What causes the Ideal L1 fault?

This fault occurs when the water inside the boiler exceeds a safe temperature, causing the system to shut down for safety. The most common reasons are a pump failure preventing water from moving through the system or a blockage caused by a build-up of sludge and debris. It can also be triggered by a faulty sensor that is incorrectly reporting the water temperature to the control board.

This fault is more common in autumn when homeowners turn their heating back on after a long summer break, as the internal pump can often become seized or stuck during periods of inactivity.

Typical repair cost £120-£350 (including labour)

DIY fix possible

Check that your radiator valves are fully openEnsure your boiler pressure is between 1 and 1.5 bar on the gaugeReset the boiler by turning the control knob to 'RE' or pressing the reset button

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Ideal models that show the L1 fault code

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

Source

Ideal L1 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026