Sime water heater shows E05; unit stops heating and may cycle on and off rapidly.

Safety: Turn off power and allow the heater to cool before touching internal components.

Steps:

• Locate DHW NTC sensor: On Sime water heaters, the domestic hot water NTC is usually clipped to the outlet pipe or inserted into a sensor well near the heat exchanger.
• Check wiring: Inspect the two-core cable from the NTC to the control board. Look for cuts, burns, or loose plugs. Reseat the connector on the board.
• Sensor inspection: Remove the NTC from its pocket or clip. Check for scale or corrosion. Clean the sensor surface and the pocket with a soft cloth.
• Resistance check (if you have a multimeter): At room temperature (~25°C), the NTC should show a resistance in the range specified by Sime (commonly 10kΩ or similar). If it reads open circuit or near 0Ω, replace the sensor.
• Reassemble and test: Refit the sensor, restore power, and run hot water. If E05 clears, the issue was likely a poor connection or faulty sensor.

Professional help: If the sensor tests good but the error persists, the control board may be faulty and should be diagnosed by a Sime technician.