A40 High

Ariston A40 Fault Code

The Ariston A40 fault code means: your boiler's main control unit has identified an internal electronic error and is preventing the system from starting to ensure your safety.. It appears on 2 Ariston models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: PCB 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 A40 fault code

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

Source

Ariston A40 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