BoilerFaultCodesWorcester Bosch 204 Fault Code
The Worcester Bosch 204 fault code means: your boiler has sensed that the water temperature has risen above the level it was set to reach, leading it to shut down for safety.. It appears on 14 Worcester Bosch models in our database.
Technical description: Current prim. water temp. higher than set val.
What causes the Worcester Bosch 204 fault?
This fault occurs when the water inside your boiler gets hotter than the temperature you have requested on the control panel. The most common cause is a lack of water flow, which means the heat being produced cannot be carried away into your radiators or hot water cylinder. This is often caused by a failing pump, a blockage in the system, or a buildup of debris inside the main heat exchanger.
This fault is more frequent when the heating is first turned on after summer, as pump components can seize up after long periods of inactivity.
DIY fix possible
Check that all radiator valves are fully open to allow water to circulate.Ensure there is enough water pressure in the system by checking the digital gauge.Restart the boiler using the reset button on the touch screen.
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Worcester Bosch models that show the 204 fault code
Click a model for the full fault code list and model-specific repair notes.
- 24/28/35 CDi MkII Repair: £120-250
- 26 CDi Xtra
- Greenstar 1000 Repair: £150-300
- Greenstar 12i System
- Greenstar 2000 Repair: £120-250
- Greenstar 27CDi Repair: £120-250
- Greenstar 28CDi Repair: £120-250
- Greenstar 30i Repair: £0-120
- Greenstar 4000
- Greenstar 8000 Life & Style Repair: £120-£350
- Greenstar CDi Compact
- Greenstar i Repair: £90-180
- Greenstar Ri
- Hideaway 90
Source
Worcester Bosch 204 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 24/28/35 CDi MkII manual (PDF)
- Worcester Bosch 26 CDi Xtra manual (PDF)
- Worcester Bosch Greenstar 1000 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026