Miswiring or Serial Communication Error

What does 0.5-second ON 0.5-second OFF mean?

This blinking pattern indicates that the serial communication signal from the outdoor unit has not been received for 6 minutes. This is a critical communication breakdown between the indoor and outdoor units, preventing them from coordinating operations and leading to system malfunction. The unit will not operate without proper communication.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Use a multimeter to check for continuity and insulation resistance on the serial communication wires.

2. 4

   Inspect communication terminals on both indoor and outdoor control boards for secure connections and any signs of damage or corrosion.

3. 5

   Check power supply to both indoor and outdoor units to ensure stable operation of communication circuits.