H 9 High

Evo H 9 Fault Code

Also written as H9 — same fault.

The Evo H 9 fault code means: your boiler has detected an internal communication error between its electronic control boards or an incorrect configuration.. It appears on 1 Evo model 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: ALTERNATING 'H9' - REFER TO FRAME 71
Typical repair cost £180-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Evo models that show the H 9 fault code

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

Source

Evo H 9 fault code information on this page is sourced and cross-checked against the official Evo service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026