Indoor/Outdoor Unit Communication Error (Outdoor Transmitting)

What does E9 (6811) mean?

The outdoor controller circuit board detects '0' receiving 10 times continuously despite transmitting '1', or it fails to find a blank transmission path for 10 minutes. This indicates potential contact failure or looseness in the indoor/outdoor unit connecting wire, a defective communication circuit on the outdoor controller circuit board, or noise interference in the power supply or connecting wire.