Medium
d.17 on Glow-worm Ultimate 3 25R

Your boiler has detected that the external heating controls, such as your room thermostat or programmer, are not communicating correctly with the system.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Heating control

From this model's manual
Verified against the Glow Worm Ultimate 3 25r installation & service manual, page 29.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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Related fault codes

d.18View →d.19View →

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