Branch Box LED 402 blinks 3 times — Serial communication error (outdoor unit or between branch boxes).

What does LED 402 (3) mean?

LED 402 flashes three times, indicating a serial communication error either between the outdoor unit and the branch box, or between multiple branch boxes.

• Loose or incorrect wiring for serial communication.
• Electrical interference or signal degradation affecting communication lines.

Click steps to track your progress.

1. 1

   Reset the power to all associated units (outdoor unit and branch boxes) by cycling their circuit breakers.

2. 2

   Check all communication wiring connections between the outdoor unit and the branch box(es) for any looseness or damage.

3. 3

   Ensure wiring connections are secure and properly insulated as per installation guidelines.

4. 4

   If the error persists, professional service is needed to diagnose the communication line or units.