BoilerFaultCodesYour boiler has detected an electrical fault with the sensor that monitors your hot water temperature, meaning it cannot heat water safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Indicates an 'open circuit' or 'short circuit' HW sensor or lead.
What causes this fault?
This fault occurs when the internal sensor responsible for tracking the temperature of your hot water fails to send a clear signal to the main control board. The most common reason is that the sensor has physically degraded over time or a wire has shaken loose, preventing the boiler from knowing how hot the water is. For safety, the boiler stops heating immediately to prevent the water from becoming dangerously hot.
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 HW light flashing — no call-out fees, no surprises.
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Ideal Response FF80 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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