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

Safety first: Turn off the Baxi air conditioner at the isolator or circuit breaker and wait at least 5 minutes before removing any covers. Risk of electric shock.

Steps to check:

• 1. Power reset: Turn off power for 5–10 minutes, then restore power and try again. Sometimes E01 is triggered by a transient communication glitch.
• 2. Inspect communication cable: Remove the indoor front cover and access the terminal block. Verify the multi-core communication cable going to the outdoor unit is not pinched, burnt, or cut. Follow it visually where possible.
• 3. Tighten terminals: At both indoor and outdoor units, check the communication terminals (often marked S, L, N or 1, 2, 3). Tighten all screws and ensure no copper strands are loose or touching adjacent terminals.
• 4. Check polarity and wiring order: Confirm the same wire colors are on the same terminal numbers between indoor and outdoor units. Incorrect polarity or swapped wires will cause E01.
• 5. Inspect PCBs for damage: With power still OFF, look at the indoor and outdoor main PCBs for burn marks, swollen capacitors, or corrosion around the communication connector. If found, the PCB likely needs replacement.

When to call a technician: If wiring is correct and secure but E01 persists, a professional should test the communication voltage and replace the indoor or outdoor main PCB as needed.