How much does it cost to fix Ideal error code F5 Or L5?

Typical repair cost for the Ideal F5 Or L5 fault is £120-200 including labour.

F5 Or L5 High

Ideal F5 Or L5 Fault Code

Q: What does the Ideal F5 Or L5 fault code mean?

Your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has safely shut down to prevent overheating.

Also written as F5ORL5 — same fault.

The Ideal F5 Or L5 fault code means: your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has safely shut down to prevent overheating.. It appears on 1 Ideal model in our database.

Technical description: Return Thermistor Fault

Typical repair cost £120-200 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Ideal models that show the F5 Or L5 fault code

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

Logic Combi C24 C30 C35 Repair: £120-200

Source

Ideal F5 Or L5 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