High
F.85 on Glow-worm Ultimate 3 25R

Your boiler has detected that its internal temperature sensors are either disconnected or have been accidentally moved to the wrong pipes during installation or maintenance work.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Fault: Temperature sensor. The flow and/or return temperature sensors have been installed on the same pipe/incorrect pipe. Temperature sensor not connected or is connected incorrectly

From this model's manual
Verified against the Glow Worm Ultimate 3 25r installation & service manual, page 34.
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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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