BoilerFaultCodesWorcester Bosch P3 Fault Code
The Worcester Bosch P3 fault code means: your boiler's internal electrical circuit has lost power because a small safety fuse has blown, preventing the system from starting up.. It appears on 13 Worcester Bosch models in our database.
Technical description: Please wait, initialisation in progress. 24 V fuse blown. Replace fuse.
What causes the Worcester Bosch P3 fault?
This fault occurs when an electrical surge or a short circuit within the boiler's internal components causes a small safety fuse to blow. The most common reason is a failing internal component, such as a sensor or the main pump, drawing too much power and triggering the fuse to protect the expensive control board. It acts like a household trip switch, cutting power instantly to prevent further electrical damage.
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 →Worcester Bosch models that show the P3 fault code
Click a model for the full fault code list and model-specific repair notes.
- Greenstar 2000 Repair: £120-200
- Greenstar 25 HE Combi Repair: £90-180
- Greenstar 25HE
- Greenstar 25i (ZWB 7-25) Repair: £200-450
- Greenstar 27CDi Repair: £120-200
- Greenstar 28CDi Repair: £120-200
- Greenstar 8000 Repair: £120-200
- Greenstar CDi Compact
- Greenstar R29 40 HE
- R30 HE Plus Repair: £0-120
- Ri 25 HE Repair: £100-180
- Worcester 25/30 HE Repair: £90-180
- ZB 7 27 HE Repair: £250-450
Source
Worcester Bosch P3 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