BoilerFaultCodesYour boiler has detected an internal communication error or a sensor problem that is preventing it from heating your home safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Appliance fault (see page 15)
What causes this fault?
This fault occurs when the boiler's main control board loses reliable communication with its internal temperature sensors. The most common reason is a failing NTC sensor providing an incorrect electrical signal or a loose connection in the internal wiring harness. Because the boiler cannot accurately verify the water temperature, it shuts down as a safety precaution to prevent overheating.
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 A5 — no call-out fees, no surprises.
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Worcester Bosch 29 HE Conventional 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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