I have an AC that I would like to control with arduino as part of a home automation project, I want to bypass the IR receiver and send signals directly to the AC controller.
How to identify which wires/ports to access? I don't even have an idea how the IR receiver controls the AC. I'm guessing it just writes "high" to appropriate wires connected to a microcontroller corresponding to IR signals received?
AC receive IR remote signals to its control board and processed by microcontroller on board and then give commands to control fan, flaps or compressor relays.
So if you want to bypass it then unplug or desolder connection to relays and connect them through arduino.
Compressor relay is bigger one with high amp ratings like 30A or so you have to figure out which relay is controlling which function then connect it to arduino.
Note arduino can't switch relays on its own as it has 5V as output high so make some switching circuit using MOSFET or transistor to switch smaller amp rating relay then control your AC relays through those smaller relays.