BoilerFaultCodesYour boiler has shut down because it thinks the water returning to the unit is dangerously hot, which usually means water isn't circulating through your radiators properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The boiler return temperature sensor has detected a return temperature higher than 105°c
What causes this fault?
This fault occurs when water is trapped inside the heat exchanger and cannot move away, causing it to overheat almost instantly. The most common reason is a failed internal circulation pump or a significant blockage in the system pipework that has stopped the flow of water entirely.
This fault often appears during the first cold spell of autumn when heating systems are switched back on after being idle all summer, which can cause internal pump components to seize.
DIY fix possible
Check that all radiator valves are fully open.Ensure the central heating pump is running and hasn't seized.Bleed all radiators to remove trapped air that might be blocking water flow.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like D4286 — no call-out fees, no surprises.
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Worcester Bosch GB162 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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