But the a.c. system on your car is fundamentally the same as on the other Escorts.
It could be an orifice tube that is partly clogged (and the high side freon pressure get too high and the compressor shuts down), or a compressor that has worn valves or just has too much muck in it from the deteriorated rubber lining of the hoses or deteriorated lubricant (and the compressor isnt really pumping the freon around very well), or having either too little lube for the compressor, or too much. More likely its a combination of things.
When the compressor is running you can expect the serpentine belt to be whipping a little ibt. The tensioner arm will likely be shaking when the compressor is on, but should be fairly 'still' under a normal idle.
We have had a hot summer here in the northeast. Today in Fairfax County VA its supposed to be 101, with no breeze worth mentioning.