How much does it cost to fix Worcester Bosch error code D4 286?

Typical repair cost for the Worcester Bosch D4 286 fault is £120-350 including labour.

D4 286 High

Worcester Bosch D4 286 Fault Code

Q: What does the Worcester Bosch D4 286 fault code mean?

Your boiler has shut down because it thinks the water returning to it is dangerously hot, which usually means the water isn't circulating properly through your radiators.

Also written as D4286 — same fault.

The Worcester Bosch D4 286 fault code means: your boiler has shut down because it thinks the water returning to it is dangerously hot, which usually means the water isn't circulating properly through your radiators.. It appears on 9 Worcester Bosch models in our database.

Technical description: The boiler return temperature sensor has detected a return temperature higher than 105°c

Typical repair cost £120-350 (including labour)

DIY fix possible

Check that your radiator valves are open and not turned to the off positionEnsure the boiler pressure is between 1 and 1.5 bar on the pressure gaugeGently bleed your radiators to remove any trapped air that might be blocking water flow

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Worcester Bosch models that show the D4 286 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch D4 286 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026