Indoor/outdoor unit communication error (Indoor unit receiving)

What does E6 mean?

The indoor controller board fails to receive signals normally for 6 minutes after power-on, or 10 minutes during operation, or from the outdoor board in twin systems. This points to communication wire contact failure, short circuits, miswiring, noise, or defects in communication circuits or fan motor/rush current resistor. It severely impairs the indoor unit's ability to coordinate with the outdoor unit.

• Open circuit or short circuit in the communication wiring (e.g., S-wire, data lines) between outdoor and indoor units.
• Faulty communication transceiver chip or opto-isolator on the indoor unit's main control board (e.g., IC U201).
• Outdoor unit failing to transmit valid communication signals due to its own internal fault or misconfiguration (e.g., Parameter P4-05 setting).
• Insufficient power supply to the outdoor unit, preventing its communication module from operating correctly.
• Incorrect or missing communication termination resistors on the outdoor unit, leading to signal loss or reflection.

Click steps to track your progress.

1. 1

   Power off and verify continuity of the communication wires (e.g., 'A', 'B', 'S') from the outdoor unit's output to the indoor unit's input.

2. 2

   Using an oscilloscope, check the communication signal output at the outdoor unit's terminal block to ensure it is transmitting valid data.

3. 3

   Measure the DC voltage across the communication lines at the indoor unit's terminal block (e.g., 0-5VDC, fluctuating) to confirm signal presence.

4. 4

   Inspect the indoor control board's communication receiver circuit (e.g., IC U201) for physical damage or burnt components.

5. 5

   Confirm the outdoor unit is receiving proper power supply by measuring its input voltage (e.g., 230VAC or 400VAC) at its main power terminals.