AEG Washer Error Code E78

The E78 error code on an AEG washer indicates that the NTC (Negative Temperature Coefficient) thermistor sensor is not seated or positioned correctly within the appliance. The NTC is a temperature-sensing component whose electrical resistance changes predictably as temperature rises or falls. The washing machine's control board monitors these resistance readings continuously to regulate water heating. When the sensor is physically misaligned or improperly installed, the readings it produces fall outside the expected parameters for normal operation, triggering the E78 fault.

Unlike NTC failure codes that point to a defective or open-circuit sensor, E78 specifically flags an installation position problem rather than an electrical fault in the sensor itself. This means the sensor may be entirely functional but is not making proper contact with the component it is meant to monitor, or it has been dislodged from its mounting point. This can occur after a previous repair where the NTC was disturbed, after significant vibration during high-speed spin cycles, or if the sensor clip or housing has worn and no longer holds the thermistor securely.

The first and most important diagnostic step is a physical inspection of the NTC's mounting location. The technician should verify that the sensor is fully seated in its designated position, that any retaining clip or bracket is intact and engaged, and that the sensor is making firm contact with the surface or housing it is designed to monitor. If the sensor has simply shifted out of place, repositioning and securing it correctly may resolve the fault without any parts replacement.