Air conditioner control, important parameters

[CambridgeMart]

As another project, I bought a faulty air conditioner that needs a new control board; of course, the board isn't available, so I need to brew my own. I've managed to decode the remote signals and know what controls are required for the fans, my remaining task is to monitor the temperatures; the output temp from the evaporator is easy as it's basically the setpoint (this unit doesn't have a remote thermostat), but there's a thermistor on the compressor discharge pipe and I don't know what temperature this should be at. My research tells me the highest temperature is the critical temperature for the refrigerant, 96.7C for R290 in this unit and the lowest temperature must be above the highest ambient temperature for the condenser to operate. What I'm after is guidance as to what end of this range I want to be aiming for.