Ariston Dishwasher Error Code AL 04

AL 04 on an Ariston dishwasher indicates a fault in the NTC thermistor circuit. The NTC (Negative Temperature Coefficient) thermistor is the sensor responsible for monitoring wash water temperature during the cycle. When the control board detects that the NTC electrical circuit has been in an open or short condition continuously for 9 seconds, it triggers AL 04 and halts operation. An open circuit means the signal path is broken and no resistance reading can be transmitted, while a closed circuit fault typically means the sensor or wiring has shorted, sending a fixed or zero-resistance signal that falls outside the expected range.

The most common sources of this fault are a failed NTC thermistor, a loose or corroded connector at the thermistor or control board, or an NTC sensor that has physically detached from its mounting point on the tub casing. Because the thermistor must be in direct contact with the casing to accurately read water temperature, improper attachment can produce erratic or out-of-range readings that the control board interprets as a circuit fault.

Diagnosing AL 04 begins with a physical inspection of the NTC sensor, its wiring harness, and connector terminals. If connections are intact and secure but the fault persists, the thermistor itself should be tested for correct resistance at a known temperature and replaced if it reads open or shorted. If a replacement NTC does not resolve the code, the timer or control module may need to be replaced, as the fault could originate in how the board is reading or processing the sensor signal.