Its not a camaro so I wasnt sure where to post so I matched the year.
Its a 78 Caprice Classic with no mods. When you switch the A/C on the compressor cluth doesn't kick on, But if you run a hot jumper to it the clutch engages. The Compressor isnt leaking nor iss everything else. Is there a relay or switch that causes the clutch to kick in when switched on inside the car? What else could be wrong?

 

There is a safety switch that prevents the compressor clutch from kicking in if the pressure in the AC system is too low. Get a freeze12 retrofit kit and some freeze12 and recharge the system. Freon is too hard tofind these days.

 

I got it figured out. It was low on juice and the compressor clutch cut out swith was bad.