How much does it cost to fix Ideal error code 4 / A?

Typical repair cost for the Ideal 4 / A fault is £150-250 including labour.

4 / A High

Ideal 4 / A Fault Code

Q: What does the Ideal 4 / A fault code mean?

Your boiler has detected that the internal water temperature is dangerously hot and has shut itself down to prevent damage or overheating.

Also written as 4A — same fault.

The Ideal 4 / A fault code means: your boiler has detected that the internal water temperature is dangerously hot and has shut itself down to prevent damage or overheating.. It appears on 1 Ideal model in our database.

Technical description: Temperature supply sensor too high (> 101 °C).

Typical repair cost £150-250 (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 4 / A fault code

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

Maximiser SE Repair: £150-250

Source

Ideal 4 / A 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