E05 on display, no hot water, boiler does not fire when cylinder is cold

Safety: Isolate electrical power and close any relevant isolation valves before removing flow switches or sensors. Expect water spillage.

Steps:

• Identify which flow switch: Some Gledhill units have a primary flow switch (for boiler circulation) and a DHW flow switch (for mains cold inlet). Check the wiring diagram to confirm.
• Check for flow: Open a hot tap fully. If the display still shows E05 and the unit does not respond, the DHW flow switch may not be detecting flow.
• Inspect wiring: Check the low‑voltage cable from the flow switch to the PCB. Reseat connectors and look for damage.
• Mechanical check: With water isolated and pressure relieved, remove the flow switch body. Inspect the paddle or turbine for limescale, debris, or damage. Clean gently and ensure free movement.
• Continuity test: Operate the flow switch manually (or blow through if turbine type) and check for continuity change across the switch wires with a multimeter. If no change, replace the flow switch.

Recommission: Refit the switch with new seals if required, open valves slowly, check for leaks, then restore power and test hot water operation.