Aircon A/C design temps?

[TorqueHorse]

Does anyone know what output temps the stock aircon system was designed for? Doesn't matter if it is an R-12 or R-134a system, I'm just curious what vent temps you are getting at the center vents (and what the delta is between ambient and what you are reading at the vent).
I recently replaced the compressor and condenser, and charged the system by weight and also the pressures look normal, per industry norms (but I can't find any specs for pressures either, only the refrigerant charge by weight).
The system cools, but at best, running down the highway, it only cools ~16 degrees C below ambient, when measured at the vent (34 degree day, 56% humidity, cooled down to 18 at the vent).
I'm debating on getting a new evaporator, but I sadly suspect the system is functioning as designed. Anyone's data driven input appreciated.

Ambient

Max cooled

[Simon_P]

The minimum vent temperature is a function of the evaporator thermostatic switch on/off temperature - I can't remember if that's in the manual but if not I can take a reading when I get mine working as I bypassed it with an electronic programmable one to make it cooler.

If you turn the fan down it should be cold enough to cycle the themostic switch and you could measure it at the vent.

The gas pressure is a function of the gas and ambient temperature - physics rather than design, but it's regulated by the trinary switch R12 has a lower operating pressure to R134a so if you have converted from R12 to R134a the cutout pressure will be a little low.

What refrigerant did you put in and did you vacuum the system first?

Your reading doesn't take account of the fan setting - the more air you pass through the evaporator the smaller the temp change.

[TorqueHorse]

Hey Simon, thanks for the response

Yes, I pulled a hard vacuum before charging the system (and it held vacuum).
I have the fan on 2 when I'm measuring the temps (set to the Recirculate position). Doesn't really seem to matter if the windows are up or down.
I'm using R-152a with POE 68 oil and a newly refurb'd compressor and new condenser, and I cleaned all the lines with AC line cleaner first and replaced all the orings with new green ones (including the ones at the expansion valve) and I could blow through the expansion valve, and the little screen at the feed side of the expansion valve was clear of debris. I had a new drier on as well, but between all my tests, the drier has been open to atmosphere for probably over a week, so I plan to replace it, but wanted to see if I needed to replace the evaporator assembly too, first.

I saw the thermostatic switch when pulling the expansion valve, but I didn't see how to test it. I tried jumping the wires that plug into the thermostatic switch, but that didn't seem to change the temps.

I couldn't see how to test the trinary switch either, only that it wasn't leaking around the threads to the drier.

I've run an elanscan with the AC on, but I couldn't find a good way to see if the compressor is cycling on/off, only that I have the AC switch on from inside the cabin.

When I have the AC turned on, the temps stay pretty consistent around the 60F mark. Both fans work at the Rad/Condenser assembly.
It will get a couple degrees (F) cooler if I'm zooming on the freeway (presumably because its getting better airflow over the condenser).

[Simon_P]

I saw the thermostatic switch when pulling the expansion valve, but I didn't see how to test it. I tried jumping the wires that plug into the thermostatic switch, but that didn't seem to change the temps.

that's what I was meaning when I said turn the fan down and see what temperature it turns on/off . You should be able to hear it. On elanscan one of the flags is A/C.

(If you don't turn the fan down it might not get cooler enough to switch the thermostat.)