9.1.7 Medium

Ideal 9.1.7 Fault Code

Also written as 917 — same fault.

The Ideal 9.1.7 fault code means: your heating system is having trouble measuring the temperature for your second heating area, which often means that specific zone won't warm up correctly.. 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: Central Heating Zone 2 Thermistor Fault.

What causes the Ideal 9.1.7 fault?

This fault occurs when the boiler loses communication with the temperature sensor dedicated to your second heating zone, such as an upstairs circuit or underfloor heating area. The most common reason is either a physical failure of the internal sensor component or a loose connection in the wiring that prevents the boiler from monitoring how hot the water is in that specific part of your home.

Typical repair cost £120-£200 (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 9.1.7 fault code

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

Source

Ideal 9.1.7 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