BoilerFaultCodesYour boiler has detected that a safety device or a control link has been triggered or disconnected, causing the system to shut down to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Jumper 8-9 not detected or external limiter has been activated.
What causes this fault?
This fault occurs when the boiler's safety circuit is interrupted, acting like a tripped fuse to prevent the unit from getting too hot. It is usually caused by an external safety thermostat detecting high temperatures or a loose connection in the wiring link on the main control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 d3 — 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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