Hello. It is so hot and I guess I forgot that last summer the ac in my car 2016 Nissan Altima S 2.4L did not seem to keep cool. Yesterday I drove 600 miles to south Texas and A/c cooled sometime and sometime not. When I got back I put my gauges on the low and the high side and got no psi. I started the car up and let it run and let ac engage and warm up anyhow i know that you have to have the valves closed until you are ready to check the psi and still nothing. So i went up to Oreilys bought one of those can kits with a gauge and came home and tried to put in the freon but it would not take any so I thought something was wrong with the gauge of the can that i bought and went back up there. The guy seem to know what he was talking about he told me that the compressor was overpressurerized and he let air out of the port and it was air not freon until the last bit which was the very last bit of freon in the system. And then he put in a half of a can. Ac no longer blows any cool air only hot air. At least before I started messing with it, there was still some cool air. Anyhow, SO I have been investigating and I find out about the Control Valve that is on the bottom of the compressor and since my compressor and my car has high mileage., I suspect it is bad. I have ordered one and when it comes in I know I will need to recover the freon before taking it out and putting in a new one, but I started thinking well maybe it is the expansion valve. So I ordered an expansion valve kit that comes with a drier, orings, expansion valve and oil. But, I cannot find the expansion valve, Is it attached to the heater core and if so, how difficult is to get to it? Or is it out there on one of the lines and I have to remove the strut tower brace to access it? Anyhow, I drive for a living and it is too hot to drive my car with no AC please help.