Ac issue

[Waterdawg1986]

Hey everyone, I’m new here, and in need of help. I have a 2007 Yukon Denali with 41,000 miles and a 6.2 liter engine. I’m an pretty mechanically inclined and usually always figure out the problem, except for this one. Haha About a year ago I noticed my ac was acting up. First thing I noticed was obviously the temp coming out of the vents. It was warmer then normal. Second thing I noticed was the electric fans were in the low speed setting and would only go into high Speed right when I turn the ac on or only when I turn the fan speed up. Other then that now the fans stay in low speed. The temp now has been fluctuating from 48 down to 40, is goes down when driving and goes up to 48 when idling.  Where as before all this happen it would stay at 40 and sometimes lower and the electric fans would stay on high. I found a leak on the Schrader valve close to the orfice tube filter and took the car to the gm dealer for them to fix it. They did and said it was low, drove away with it thinking it fixed. But no, it wasn’t. It was blowing humid air now. Took it back and they said they didn’t charge it up enough. Still acts the same Where the temp goes up and down even though it has been completely evacuated and fully charged up. So I took it to another gm dealer and they did a diagnosis and evacuated and checked the pounds and found nothing wrong. I have changed the high and low pressure sensors and changed the relays for the fans and still the same. I’m thinking there is a faulty sensor And that’s why the valve started leaking in the first place because of high pressure because of the fans not coming on when they needed to. What do you all think? Help me