They are selling AC service kits everywhere but in the grocery store. They make it sound so easy and it generally is except when you run into problems. It is impossible to troubleshoot your AC using only one gauge; you need to know the low and high pressure and the difference is the most effective way to find a problem. When you hook up your kit if the gauge reads low it is OK to add Freon until the pressure reaches the normal area. If it does not increase as you add Freon or goes high quickly then I suggest it is time for a pro. You can do serious and expensive damage and may even cause some bodily harm. Safety is key to servicing AC always wear gloves and a facemask, Freon is COLD and will freeze skin on contact and believe me it hurts. The 134 connections are better than the old R12 screw on connections but accidents can happen very quickly. Many times the high and low side are confused but it is simple to tell them apart. The low side is the larger of the 2. Do not hook up to the wrong line.If you do have a problem visit our forums, I can sometimes help by knowing the temps of hoses or if some are frosting up. 9 times out of 10 AC repairs are quite simple and can be performed by a competent DIY