Try a couple of things before panicing.
With the engine off, reach down and try to turn the compressor. With the clutch disengaged, it should easily turn over by hand - and listen/feel for anything rough or binding.
Find the drier/accumulator and find the two sensors that are screwed into it.
The low-pressure switch has two spade plugs directly on it (the fan switch is different, it has two 4" wires attached directly to it, and the spade plugs on the end of those). Unplug the two low-pressure switch wires, crank the car, start the AC, and short the two wires you removed from the low-pressure switch together with a paperclip or something. The compressor should run.
If it does, check the sight glass on the top of the drier for bubbles or evidence of freon flowing. If all is okay and sounds fine, let it run a short while to see if the low-pressure hose gets cool. If it does, it may be a bad pressure switch - or a lot of other things also. next step is to check pressures with a gauge set.

If the compressor does not run with the swich wires shorted, it may be a fuse, or the mAS relay controller (or you may have a separate relay on your '86, I can't remember. But check the fuse compartment.

Try these and get back to us.