if you need a refill you may have a leak somewhere.

Buy the r34 refill with the gauge on it. Most cars require around 32-36psi of freon.

btw, if you do have a leak use mighty putty to seal it if its on the aluminum pipes.....

If you want, im going to my in-laws this weekend so if you want to meet me in bethlehem I'll help you out. I also have a few cans of r34 refill that I never used......
ohh and mighty putty.