6-5 Medium

Ideal 6-5 Fault Code

Also written as 65 — same fault.

The Ideal 6-5 fault code means: your boiler is having trouble communicating with your wall-mounted thermostat, which is preventing it from knowing when to turn the heating on.. It appears on 1 Ideal model in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Room Stat 2 Fault
Typical repair cost £120-250 (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 6-5 fault code

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

Source

Ideal 6-5 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 7 July 2026