Display shows E09, indicating sensor error (supply temperature sensor or return sensor)

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Open or shorted NTC sensor, Damaged sensor wiring, Poor sensor contact with pipe or well, Faulty main control board input

Safety: Turn off power before testing sensors.

Steps:

Inspect sensor wiring: Check for cuts, loose connectors, or corrosion at the sensor terminals.
Measure resistance: Use a multimeter to measure sensor resistance and compare to Riello temperature/resistance chart. Replace if out of range.
Ensure proper mounting: Confirm the sensor is firmly attached to the pipe or fully inserted into the well with thermal paste if required.

If E09 persists with new sensors, the main control board may be defective.

Medium 3/5

NTC Temperature Sensor

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