Hello my ac in my 82 has not been blowing as cold so I boug hy a can of 134a and before I connected the hose I noticed that the low pressure port on the compressor was loose so I'm guessing that's why it not cold anymore. I did convert it to the 134a low pressure port, anyway when I try to put the freon in it will not go in like it's blocked, is there anyway to change that low pressure port and recharge it by myself or do I need to take it to a professional