High
26 on Chaffoteaux Calydra 24 Green

Your boiler has lost communication with the temperature sensor inside the hot water cylinder, meaning it can no longer monitor how hot your water is.

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.

Technical description

Thermistor cylinder bypassed

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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