BoilerFaultCodesYour boiler has encountered a computer glitch on its main control board and cannot function until it is reset or repaired.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Internal error.
What causes this fault?
This fault occurs when the boiler's internal computer suffers a communication failure or data error between its electronic components. The most common reason is a temporary electrical surge or a physical degradation of the circuits on the main control board, which prevents the boiler from safely managing the ignition and heating process.
DIY fix possible
Press and hold the 'Reset' button for five secondsWait for the boiler to restart and monitor if the code reappearsEnsure the power supply to the boiler is stable and not fluctuating
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like F0 — no call-out fees, no surprises.
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Worcester Bosch Greenstar 25i (ZWB 7-25) is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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