First you should not just dump in more refrigerant, too much will have an adverse effect on the systems ability to cool the car down every bit as much as not enough would.

Question. Do you have the air set on recirculate? That is the MOST efficient setting and the one that would get you the coldest vent temperature.

50f vent temps at idle, with 90f ambient is within normal expectations. On the highway I'd like to see 40f, but again some cars simply wont reach that every day because of humidity, ambient temperature, and sun loads that the system needs to overcome.

The first thing you do is find yourself a reputable A.C.
repair shop and have them check the head pressure. Before that you might want to take a garden hose and wash out your condencing coil. DO NOT use the freon recharge kit you buy from the store. That can is " RED TAC " a propane
mixture and is not compatable with the 134A in your system. To use the redtac you have to completely empty and recover all 134A and evacuate it. Then refill it with the
redtac. Read the fine print on the can. A.C. whether in a car or the home is NOT a d.i.y. project. If your ambiant temp is 90 degs. your gauge will show over charged. If the
ambiant temp is 60 degs your gauge will show under charged.
Same holds true for the inside temp of the car. To recharge an A.C. unit in a car the proper way is to completely evacuate it and put in a new charge. How do you know you are a lb. low ? How do you know if your 8 oz. low ? How do you know if your over charged ? How do you know that your compressor valves aren't leaking and you have the proper charge ? Those are just a very few things that have to be considered. Then there is the electrical
system. That will be next weeks movie. Good luck

Thanks. I took it to Tuffy... they charged me a hundred dollars to recharge it. Said it was low on freon. I don't know if that's true or not, I don't notice a difference in performance... but it does work just not freeze me out of the car like I want. I guess I'll just live with it until or unless it quits.

ok, they sucked out the old freon and added back the proper amount. they discussed the test results, such as vent temp at idle and system pressure? did you tell them it worked the same before and after? what was their response? you need to show a little initiative or at least some knowledge to have a rational discussion with the tech.

Last summer we had a new A/C compressor, reciever/dryer, and oriface tube replaced on our SUV. When the shop got done we drove it home, but the air blowing out of the vents was barely blowing cold air. I took it back to the shop the next day and they investigated it. Turned out, the mixing door for heat/cool was not working. The tech told me he could fix it, but it was probably something I could fix myself and save some money.
Some day I may actually fix the mixing door.
My solution for now was to disconnect the heater core using a system of valves. Close two valves going to the heater core and open a valve to allow coolant to bypass the heater core and flow on thru the system.
Yes I realize it is a redneck solution, but it works.

Pooh Bear