High
91 on Keston 30C

Your boiler has detected a problem with the internal sensor that monitors the temperature of water flowing through the system, preventing it from heating up.

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

NO WATER FLOW THERMISTOR FAULT - CONTACT INSTALLER

From this model's manual
Verified against the Keston 30c 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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Related fault codes

92View →93View →E15View →

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