BoilerFaultCodesHalstead E04 Fault Code
The Halstead E04 fault code means: your boiler has stopped working because the water pressure inside the heating system has dropped too low to operate safely.. It appears on 6 Halstead models in our database.
Technical description: Inadequate system pressure
DIY fix possible
Locate the external filling loop, which is usually a silver flexible hose connected to two valves under the boiler.Gradually open the valves to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly to stop the flow and ensure the boiler resets itself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Halstead models that show the E04 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Halstead E04 fault code information on this page is sourced and cross-checked against the official Halstead service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026