Miswiring or Serial Communication Error

What does 0.5-second ON 0.5-second OFF mean?

This blinking pattern indicates that the serial communication signal from the outdoor unit has not been received for 6 minutes. This is a critical communication breakdown between the indoor and outdoor units, preventing them from coordinating operations and leading to system malfunction. The unit will not operate without proper communication.

• Physical damage (e.g., cut, pinch, loose terminal) to the serial communication cable (CNV, CMV, CNP) between the indoor and outdoor units.
• Incorrect wiring sequence or polarity reversal on the communication terminals (e.g., TB7) during installation or maintenance.
• Excessive cable length or improper cable type (e.g., unshielded cable in an EMI-rich environment) leading to signal degradation.
• Malfunction of the communication transceiver chip on either the indoor or outdoor P.C. board.
• Power supply issue to the outdoor unit (e.g., complete loss of outdoor power) preventing it from sending communication signals.
• Incorrect DIP switch settings (e.g., SW1, SW7) for system addressing or master/slave configuration.

Click steps to track your progress.

1. 1

   Disconnect main power to both indoor and outdoor units.

2. 2

   Verify the serial communication wiring (CNV, CMV, CNP) between the indoor and outdoor units for proper connection, polarity, and terminal tightness (e.g., at terminal block TB7).

3. 3

   Use a multimeter to check for continuity on each communication line and for any shorts between lines or to ground. Measure resistance between communication lines (e.g., CNV-CMV, CMV-CNP) to ensure correct termination resistance if applicable.

4. 4

   Power up the outdoor unit only and use an oscilloscope to check for the presence and integrity of the communication signal (e.g., pulsed waveform) on the outdoor unit's communication terminals (TB7).

5. 5

   Check all relevant DIP switch settings (e.g., SW1 on indoor, SW7 on outdoor) to ensure correct system addressing and operational mode.

6. 6

   If the communication signal is absent or garbled from the outdoor unit, or not received by the indoor unit despite healthy wiring, consider replacing the outdoor control P.C. board and/or the indoor control P.C. board.