BoilerFaultCodesWorcester Bosch d3 Fault Code
Also written as D3 — same fault.
The Worcester Bosch d3 fault code means: your boiler has lost its connection to an external safety device or a plug-in controller, causing it to stop running as a safety precaution.. It appears on 31 Worcester Bosch models in our database.
Technical description: Jumper 8-9 not detected.
What causes the Worcester Bosch d3 fault?
This fault occurs when the electrical bridge that completes the safety circuit between the boiler and its external controls is broken. It is usually caused by a loose connection in the wiring, a faulty plug-in wireless receiver, or the small link plug falling out of place. Because the boiler can no longer verify that it is safe to operate, it shuts down immediately to prevent uncontrolled heating.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Worcester Bosch models that show the d3 fault code
Click a model for the full fault code list and model-specific repair notes.
- 533 Compact
- 535 Compact
- 537i Repair: £120-250
- Bosch Greenstar ZWBR 7-25A
- CDi Highflow Repair: £120-250
- Greenstar 2000 Repair: £100-200
- Greenstar 24
- Greenstar 25 Si Compact Repair: £90-180
- Greenstar 25HE Repair: £80-180
- Greenstar 25i (ZWB 7-25) Repair: £120-220
- Greenstar 25Si Compact ErP Repair: £90-180
- Greenstar 27i System Compact ErP Repair: £90-180
- Greenstar 28
- Greenstar 28CDi Compact ErP Repair: £90-180
- Greenstar 30 Si Compact Repair: £90-180
- Greenstar 30HE Repair: £90-180
- Greenstar 30i System Compact ErP Repair: £90-180
- Greenstar 30Si Compact ErP Repair: £90-180
- Greenstar Highflow Repair: £90-180
- Greenstar R 28 HE System Repair: £90-180
- Greenstar R29 40 HE Repair: £100-250
- Greenstar System Repair: £120-250
- Greenstar ZWB7 Repair: £100-200
- Highflow 400 Electronic BF
- Highflow 440 CDi Repair: £150-300
- Highflow 550 CDi Repair: £150-300
- Highflow CDi Repair: £150-300
- R30 HE Plus Repair: £90-180
- Worcester 25/30 HE Repair: £90-180
- ZB 7 27 HE Repair: £120-220
- ZWB 7-25 Repair: £100-200
Source
Worcester Bosch d3 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
- Worcester Bosch 535 Compact manual (PDF)
- Worcester Bosch 537i manual (PDF)
- Worcester Bosch Bosch Greenstar ZWBR 7-25A manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026