I am looking for the FSM excerpt or chart that shows what the AC vent temp should be given a certain outside temp/humidity and gauge pressure readings.
Just wondering. Have you tried a Google search for "freon r134a temperature pressure chart"?
However, my gauges have the pressure temperatures right on the red inside scale of the gauge itself. No searching required. Just read the temperature directly off of the red scale on the gauge.
I have an old set of r22 gauges with new hoses and rebuilt valves...so the gauges read pressure well, but the markings are not correct. I have one for my Grand Cherokee, but I figure every vehicle has one of their own as the vent time will fluctuate some I figure.
The evap and condensing pressures/temperatures are determined by the Cooling fluid type (Freon). So no matter what car it is, for R134a the temperature/pressure charts will be the same.
Now different cars may have different "Delta T" values as the design of the system does affect the target Delta T temperatures.