Don't be so quick, please, in questioning my honesty. I take that seriously but will disregard that comment.

Since we're getting deeper into the subject than simply adding refrigerant, I will tell you what I know about the history of my AC system, which isn't much. I don't pretend to know much about AC systems (as is obvious from my basic questions), and I'm not trying to hide anything. I'm just trying to find an economical way to getting cooler air out of my air vents...

The AC system has not been opened during my ownership of the car, which has been just over 2 months now. I personally didn't touch the AC system or requested any repairs made so far. When I bought the car from the previous owner, it was April, and it was moderately warm outside, and at that time, the AC system was producing cool air. It wasn't cold, but it was cool enough to chill the interior - I didn't measure the temperature.

Now that it's gotten hot out, the system cannot keep up. It delivers sort of room-temperature air (cooler than outside air, but not cold enough to have any effect on cooling the interior). The previous owner told me that the AC system "could certainly perform better - might need a charge of Freon". I haven't used the AC since it's gotten hot out because it's useless to run it when it doesn't do anything for me.

Since I've never serviced an AC system, I blindly assumed that it must need more refrigerant. I didn't know about that website - thanks for pointing it out; I will read it. I had concerns about adding oil. I do know that too little or too much oil are both bad, so that was the reason for asking question #1. I guess there isn't an easy way to answer that question without evacuating the system completely and doing a fresh fill.

I understand that the proper procedure would be to leak-test and, if there is a leak, to recover the refrigerant, fix the leak, flush, evacuate, and refill, but certainly I don't have the equipment to do that, nor do I pretend to have any knowledge about carrying out that procedure properly.

However, even with my lack of knowledge and equipment, couldn't I start the diagnostic process by measuring the pressure at the low-side port? If it's low, I guess that would point to a leak, and if it's normal, I guess it would point to something else. I've seen a couple tester gauges at autoparts stores for measuring the refrigerant pressure in the system. Couldn't I do that first and go from there?

And cut the newbie a little slack, will ya please? Just trying to learn, like everyone else