The AC in my car was working fine until one day I decided to put a134a gauge on the low side port it to check the level of refrigerant.In about 3 days all the refrigerant leaked out slowly. So I bought more refrigerant to go and that time the low side would not allow any in it just spit out the side of the 134a hose. I think it is possibly the hose it's self or the valve in the low side damage. My car has a retro fitting piece on the low side port. So when you put the hose on the port the valve on top pushes the other valve at the bottom down. Any ideas also is the valve that go in the low side port the same type that goes in tires