E08 displayed, immersion heater does not operate even when selected

Danger: Immersion circuits are 230V and can draw high current. Isolate power at the consumer unit and fused spur before removing any covers. Verify isolation with a tester.

Checks:

• Manual reset: Many Gledhill immersion thermostats have a small reset button under the cover. With power off, remove the cover and press the reset. Refit cover before restoring power.
• Visual inspection: Look for signs of overheating at the immersion terminals or wiring. Any charring or melted insulation requires replacement of the affected parts.
• Element continuity: With power off and wires removed from the element, measure resistance across the element terminals. A typical 3kW element reads around 18Ω. If open‑circuit, the element has failed.
• Thermostat test: Check continuity through the thermostat when set above ambient temperature. If open when it should be closed, replace the thermostat.
• PCB/contactor: If the element and thermostat are sound but no power reaches the immersion when called, the PCB relay or external contactor may be faulty and require replacement.

Note: Always ensure the cylinder is full of water before energising an immersion heater to avoid dry‑firing and element failure.