How much does it cost to fix Ideal error code F4 Or L4?

Typical repair cost for the Ideal F4 Or L4 fault is £120-220 including labour.

F4 Or L4 High

Ideal F4 Or L4 Fault Code

Q: What does the Ideal F4 Or L4 fault code mean?

Your boiler has stopped working because it is having trouble reading the temperature of the water flowing through it, so it has safely shut down to prevent overheating.

Also written as F4ORL4 — same fault.

The Ideal F4 Or L4 fault code means: your boiler has stopped working because it is having trouble reading the temperature of the water flowing through it, so it has safely shut down to prevent overheating.. It appears on 1 Ideal model in our database.

Technical description: Flow Thermistor Fault

Typical repair cost £120-220 (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 F4 Or L4 fault code

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

Logic Combi C24 C30 C35 Repair: £120-220

Source

Ideal F4 Or L4 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