BoilerFaultCodesYour boiler is not receiving a signal from your thermostat or internal timer telling it to turn on.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: No heat demand (check thermostat/programmer) or red diode damaged.
What causes this fault?
This fault occurs when there is a break in the communication link between your controls and the boiler's main computer. It typically happens because the mechanical timer has worn out or the batteries in your wall thermostat have died, meaning the boiler never receives the 'on' command. In some cases, the internal electronic board that processes these signals has developed a fault and can no longer recognize when heat is being requested.
This issue is frequently seen during the first cold snap of autumn when homeowners try to turn their heating back on after it has been switched off all summer.
DIY fix possible
Check that your room thermostat is turned up higher than the current room temperature.Replace the batteries in your wireless room thermostat if it has them.Ensure your programmer or timer is set to 'ON' or 'AUTO' and that the clock is showing the correct time.
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A boiler cover plan would cover faults like FAIL POINT D — no call-out fees, no surprises.
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Worcester Bosch 25si and 28si 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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