For 3 months I had little to no A/C. I bought a can of r-134a with a meter and it gave me a border line reading, but when I pressed the button to charge the system, pressure would build up and not go into the system so that when I released the valve connection the refrigerant would spray out from the pressure that built up between the can and the car's valve. After several frustrating and anxious attempts, I noticed that the right side was blowing cold air but not cold enough for Florida and the driver's side was only cool if anything. I was reluctant to bring it to the dealer because it was something I knew was simple and they would have charged well over $100. How could I get an accurate reading from the guage yet nothing would flow the other way into the car? Here is what I learned. I have to not only connect the valve (the sleeve locks properly) but I also have to actually grasp from the underside of the valve (so as not to risk bending the A/C line) and press down from the top. If I apply enough pressure straight down on the valve connection AND hold the can upside down, it works! I am so happy to have cold air on both sides. The right side is still colder than the driver's side, but that's how it was when I bought the car brand new on March 31, 1997. I could have put more r-134a in, but it was reading right in the middle of where it should be and it is now plenty cold. Why should I have had this situation? Why would I have to grasp the connection and apply pressure to the valve connection? Also, why don't they tell you to hold the can upside down? When you do, you can actually feel the cold going into the car.