Hi, I accidentally released a small unknown amount of refrigerant after which my 2001 3500 AC seemed to still cool at about the same level as before and remained that way for the last year until the current heat wave during which it still cools but not enough. I'm sure I used the 18 oz recharge kit properly emptying the canister and the AC was definitely cooling better.
The problem is that the initial pressure reading on the kit was 35 psi and so was the ending pressure. A different gauge after recharge also indicated 35 psi. At ambient temp above 90 I was shooting for 45 psi. I'm sure my readings were correct so how could I start at 35 psi, empty 18 oz's, get better cooling and end at same 35 psi? System is not leaking holding at 35 psi for weeks. Although improved it seems I used to get a little better cooling but am afraid to add more refrigerant until I understand why pressure remains at 35 psi- I don't want to overcharge the system. Thanks for any info.

Yes- every reading. On an auto AC forum I was told pressure readings are "a crap shoot" which doesn't make much sense to me but I know little about the subject.

A year ago I was working elsewhere on the engine and leaned on an AC line causing a hair line crack at a soder or weld joint. A fine green mist came out and for about 2 minutes I did nothing figuring it off to a repair shop. I lifted the line back up and the leak stopped- no soapy water bubbles test. I strapped the line up and put a rubber sleeve on the crack followed by a c clamp. AC was still cold after that (the reason I labeled the leak "small") until the heat spell this year where it still cooled but not like last year.
The van was converted to high top medical transport new directly from the factory and an after market rear AC was added and I could find no records of correct weight of refrigerant so pressure and performance seem the only way to go.
From what I recall pre-leak I'm now only slightly less cool but that's still slightly uncomfortable in hot S. Florida. I plan to add a few ounces a day up to a max of another 12 ounces to see if I can get there.
I don't think this is an issue everywhere but chances are where I live if you go into an AC shop for a top off charge your coming out with no cooling at all and AC problems you didn't have before you went into the shop. I'm not ragging here that's just how dog eat dog it is here.