How much does it cost to fix Ariston error code A 40?

Typical repair cost for the Ariston A 40 fault is £250-450 including labour.

A 40 High

Ariston A 40 Fault Code

Q: What does the Ariston A 40 fault code mean?

Your boiler's main computer control panel is experiencing an internal electronic failure, which is preventing the system from operating correctly.

Also written as A40 — same fault.

The Ariston A 40 fault code means: your boiler's main computer control panel is experiencing an internal electronic failure, which is preventing the system from operating correctly.. It appears on 2 Ariston models in our database.

Technical description: MCU fault 2

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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Ariston models that show the A 40 fault code

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

Euro Combi 30 MFFI Repair: £250-450
Euro Prisma 24 Repair: £250-450

Source

Ariston A 40 fault code information on this page is sourced and cross-checked against the official Ariston service / installation manuals for each affected model.

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