I've used them with good success on systems that were in good shape. That said, if the dealer did re-charge and it didn't get much better, I'd guess you have something else wrong besides the R34 charge (or possibly overcharge). You could also have a plugged expansion valve, or non-condensibles (i.e. air) in the system

Your system should have a sight glass (my 2001 is located down in front of the radiator, just in front of the battery on the driver's side). It's a small round glass "window" pressed into a square aluminum fitting on top of a round tank (the receiver/drier). I'd look up the symptoms in the FSM, (sticky'd on this site), and then fire up your A/C and watch the sight glass for comparison.

Beyond that, you need someone with an A/C gauge manifold and some knowledge of A/C systems to diagnose the exact problem. Good luck! <img src="/forums/images/graemlins/patriot.gif" alt="" />