Since I now have an easy access to that CN7 connector, I decided to hookup my oscilloscope to see if there is any signal on pins 2, 4 and 6.

I connected my Rigol DS1054Z and checked for any possible signal or change of tension when:

• connecting the air conditioner to main AC
• turning on the air conditioner
• turning off the air conditioner
• pressing a button from the IR remote control

Sadly this test didn't bring me any result. Once the air conditioner is connected to the main AC these 3 pins are at a 5V state and don't change. I also probe the 12V and NC pins but as expected just a constant 12V once the air conditioner is powered up and absolutely nothing on the NC pin.

I started to doubt that this old air conditioner could be connected to CS-NET via H-LINK but after digging in that site I previously found, I found this schematic/wiring diagram.

It is clear that this air conditioner can be connected to CS-NET via H-LINK. I will just have to keep playing detective for a bit longer and keep looking for clues.