Eldom digital heater shows E09; water may overheat or not reach set temperature.

Safety: Overheating can cause scalding and tank damage. Turn off power and allow the unit to cool.

Steps:

• Locate thermostats: Many Eldom heaters use a primary control thermostat/NTC plus a secondary safety thermostat mounted on the element flange or tank surface.
• Check continuity: With power off and wires removed, measure continuity across the safety thermostat. It should be closed (0 Ω) at normal temperature. If open and not resettable, replace it.
• Check for stuck-closed condition: If water is overheating, verify that the control thermostat or NTC is correctly sensing temperature and that the safety thermostat opens at its rated temperature (requires controlled heating and monitoring; usually done by a technician).
• Verify wiring: Compare wiring to the Eldom schematic on the heater cover. Correct any miswiring that bypasses safety devices.
• Replace faulty thermostat: Install a new Eldom-compatible safety thermostat if defective.