Very well said, gentlemen. Mitsu guy here - 12-24dc fluctuating on S2/S3. Outdoor sends 24vdc, indoor responds with 12vdc. That’s how you troubleshoot. Also, fun fact although I’m not sure if it’s true, but they are able to share the S2 wire because AC travels on the outside of the line and DC travels in the middle.
It would be nice if the manufacturers would agree on communications protocols. For those who might wish to delve further into how to create a list of those protocols for the IR remotes, you could consider programming an arduino to read the signals from different remotes and creating a chart showing what each button does for each manufacturer, then converting that signal using the arduino programming. This would, of course, be an exercise for those who wish to understand this better. This link explains this process and also how a person could easily use their phone to see the IR light coming out of your remote if you don't happen to have an IR scope. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-8E3ltjnbV0c.html Now if we could just get those manufacturers on board so that the technician could see the signal with the oscilloscope then verify that the PWM is correct rather than just seeing if it is there.
