86 air conditioning problem
 

compressor is working after i wired around just to make sure it is functional. I am sure it turned off due to low freon. I went to install r12 and negative vac immediately on gauge. Where is the most probable place for obstruction in line? I assume that has to be the issue. any thoughts. thanks.

Maybe orifice tube or expansion valve, usually I like my AC to be reliable, so I have the system flushed, replace the orifice tube and receiver dryer, pull a strong vacuum a few hours to check for leaks, then refill.

usually the receiver drier gets corroded internally and then plugs,

NOTE if your going to flush the system then do it before you replace any of the O rings then make sure the system is chemical free before installing the new O rings as the chemicals will distort the the O rings and they will leak soon after they are fitted