Indoor unit will not start; display shows E01 shortly after power-on.

Safety first: Turn off the air conditioner at the breaker and isolate power before removing covers. Use a non-contact voltage tester to confirm power is off.

• Step 1 – Power reset: Turn off the breaker for 5 minutes, then restore power. Try starting the unit again to rule out a temporary logic fault.
• Step 2 – Inspect communication cable: Remove the indoor front panel and access the terminal block where the interconnecting cable (often labeled 1–2–3 or L–N–S) connects. Check for loose screws, burnt terminals, or broken insulation. Tighten all terminal screws firmly.
• Step 3 – Check polarity and wiring order: Compare the wiring order at the indoor unit to the outdoor unit terminal block. Ensure the same color wire goes to the same terminal number at both ends. Correct any mismatched connections.
• Step 4 – Look for cable damage: Trace the interconnecting cable along its route (as far as accessible) and look for crushed, cut, or water-damaged sections. If damaged, replace the cable with the same gauge and type recommended by Ariston.
• Step 5 – Board inspection (advanced): With power still OFF, remove the indoor PCB cover. Look for burnt components, swollen capacitors, or signs of moisture. Do the same at the outdoor PCB. If any damage is visible, the corresponding PCB likely needs replacement.
• When to call a technician: If wiring is correct and intact but E01 persists, a professional should test communication voltages and replace the indoor or outdoor main PCB as needed.