BoilerFaultCodesYour boiler is struggling to accurately measure the temperature of your hot water, which usually means your taps will only run cold or keep fluctuating in temperature.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Hot water NTC sensor defective.
What causes this fault?
This fault occurs when the internal sensor responsible for monitoring hot water temperature starts sending incorrect readings or stops working entirely. The most common reason is that the sensor has suffered a terminal electrical failure or has become heavily corroded after years of constant heat cycling.
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.
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A boiler cover plan would cover faults like A7 — 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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