Hello Don:

One of the chief reasons that compressors don't come on is because the freon charge is low. There is a pressure switch on the receiver/dryer (upright cylinder near the passenger side firewall under the hood. Remove the pressure switch from the r/d, and jumper the connections with a piece of wire with the a/c controls set to max and air on. Now the compressor should run. Don't do this for more than a few seconds because if the charge is low this will ruin it...

If the compressor runs, then you need to start looking for a leak. Mine did this recently-- the relay that runs the aux fan in front of the rad cooked, the a/c system got hot, the pressure went up and blew out the condenser-- $$$ ouch!

Let's hope yours is something simpler-- I had mine converted to R12a because freon no longer available here...