BoilerFaultCodesYour boiler has detected a problem with the sensor that monitors hot water temperature, which often means it cannot heat water correctly or has stopped for safety.
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 17)
What causes this fault?
This fault occurs when the boiler's internal computer loses communication with the sensor that measures your hot water temperature. The most common reason is that the sensor has physically failed or developed a short circuit, but it can also be caused by loose or damaged wiring connecting the sensor to the main control board. Because the boiler no longer knows how hot the water is, 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 A7 — 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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