High
FAIL POINT G on Worcester Bosch Greenstar 25Si

Your boiler has shut down because it is running too hot, likely due to low water pressure or trapped air in the heating 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.

Technical description

Primary Overheat: Boiler not fully water pressurised, air in system, pump failure, primary sensor not correctly fixed, or overheat thermostat short circuit across ST16 contacts 5 & 6.

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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