High
6 flashes on Worcester Bosch Greenstar 25CDi

Your boiler's temperature sensor is failing to communicate correctly, which prevents the system from knowing how hot the water is and causes it to shut down for safety.

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

CH flow NTC sensor defective. Check CH flow NTC sensor and connecting lead.

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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