1999 Caravan with ac trouble

I have a 3.0 engine with a single front ac unit. When you start putting freon in the compressor will lock up only after about 1 can of freon. I had my gauge set on the high pressure port and it only slightly raised as the conector on my small can hookup blew apart on the low pressure side. The compressor,after a full vacuum, will come on after adding about 1/4 of a can of freon. High pressure lines are extremly hot after a minute of running, low side line is warm. Then all of a sudden the compressor will start sqiling the belt until i turn it off. I have dissconnected the lines up to the expantion valve at the firewall and blew trough everything with comppresed air. Could my trouble be the valve or should i be looking for something else???? Thanks for reading and posting your thoughts.

Sure sounds like a problem with the expansion valve.