AC compressor clutch doesn't engage

Hi, I have at 94 explorer w/ 4ltr v 6 -- my current problem is that when the AC is turned on the compressor does not engage -- any suggestions? the AC was working fine a couple months ago. I'm thinking possible electrical? Any advise -- tests? Thanks!

Can you hear the engine surge as if it is trying to kick in?
Can you spin the clutch on the compressor by hand? If not then clutch may be gone, thus compressor may be gone.
But, best guess is that you need the system recharged. Get a shop to throw a guage on it and go from there.

Thanks...i'll check that out...will the system not engage if it is too low?

Yes, that was what I was told. Have some guages put on it and look for leaks on the lines etc.