6603 (A3) Transmission bus BUSY error

What does 6603 (A3) mean?

This error signifies that the transmission processor is unable to transmit data because the transmission line is busy. This can be caused by short-cycle voltage noise, an increased amount of transmission data due to miswiring, or a malfunction in a repeater.

• Short-cycle voltage such as noise mixed on the transmission line.
• Increase of transmission data amount caused by a miswiring of terminal block (TB3) and terminal block (TB7) on the outdoor unit.
• Malfunction of repeater on the outdoor unit.

Click steps to track your progress.

1. 1

   Turn off the power to the outdoor unit and any associated centralized control systems.

2. 2

   Inspect the transmission lines and terminal blocks (TB3 and TB7) on the outdoor unit for any miswiring or loose connections.

3. 3

   Check for potential sources of electrical noise that might be interfering with the transmission line.

4. 4

   Restore power after verifying connections and addressing potential noise sources.

5. 5

   If the error persists, a qualified technician should investigate the transmission processor and any repeaters.