High Lockout
9.3 on Worcester Bosch Greenstar 25HE

Your boiler’s internal computer has encountered a memory error and cannot safely operate the heater.

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

GFA-Asic-error

What causes this fault?

This fault occurs when the boiler's main control board experiences an internal memory failure, meaning it can no longer communicate with the safety software. It is typically caused by a microchip hardware failure or an electrical surge that has corrupted the internal data. Because the computer can no longer guarantee the boiler is running safely, it shuts down the entire system as a precaution.

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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