Indoor/outdoor unit communication error (Outdoor unit transmitting)

What does E9 mean?

This indicates a communication error where the outdoor unit transmits but receives a continuous '0' (30 times) or fails to find a transmission path for 10 minutes. Common causes include wiring issues between indoor/outdoor units, noise interference, or a defective communication circuit on the outdoor controller board. This prevents crucial operational data exchange, leading to system shutdown or erratic behavior.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Investigate potential sources of electrical noise entering the power supply or communication wires.

2. 4

   If the abnormality persists after the above steps, replace the outdoor controller circuit board.