How much does it cost to fix Ideal error code 400?

Typical repair cost for the Ideal 400 fault is £250-450 including labour.

400 High

Ideal 400 Fault Code

Q: What does the Ideal 400 fault code mean?

Your boiler's internal computer has encountered an electronic error and is unable to communicate with its controls to provide heat.

The Ideal 400 fault code means: your boiler's internal computer has encountered an electronic error and is unable to communicate with its controls to provide heat.. It appears on 2 Ideal models in our database.

Technical description: internal failure - electronic

What causes the Ideal 400 fault?

This fault occurs when the boiler's main control board experiences a critical hardware failure and can no longer process instructions. It is usually caused by a component on the circuit board wearing out over time or being damaged by a sudden electrical surge. Because the 'brain' of the boiler has failed, it can no longer safely manage the gas valve or ignition process.

Typical repair cost £250-450 (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 400 fault code

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

Source

Ideal 400 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