Be SURE to replace the drier (about 50.00)this is the filter for the system. While you are at it DRAIN THE OIL OUT OF THE COMPRESSOR AND REFILL WITH OIL FOR A R134 Evacuate the system and add the proper amount of oil to the lines, 2 ounces for the drier, maybe another couple of ounces if the system was leaking. Then evacuate the system, if not you wont have cold air and will replace everything again shortly