High
86 on Ideal Isar M30 / M100

Your boiler is receiving an confusing signal from the pipe that brings water back from your radiators, so it has paused operation to prevent any potential strain on the system.

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

RETURN TEMPERATURE SENSOR

From this model's manual
Verified against the Ideal Isar M30 M100 installation & service manual.
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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