Error 15 — Communication fault between indoor and outdoor unit

What does 15 mean?

The outdoor unit control board cannot communicate with the indoor unit control board. This can be caused by wiring issues or a faulty PCB.

• Bad communication wiring
• The PCB is bad
• Incomplete or inadequate ground

Click steps to track your progress.

1. 1

   Ensure communication cable connections (terminals 3/C and 1) are tight and on the correct terminals.

2. 2

   Check that the communication cable (14/4 stranded copper) is not spliced and PCB connections at CN21 are good.

3. 3

   Verify the ground connection.

4. 4

   Check for proper voltage between communication 3 and N at indoor and outdoor terminal blocks.

5. 5

   Replace the communication wire if ok.

6. 6

   Replace the PCB if the issue persists.