93 mustang ac problems

My car runs fine without the air conditioning on. When you turn it on however, it doesnt want to idle. It just dies. If I keep the gas going, it wont die also. What can do I to fix this problem or what should be replaced?

Sounds like the compressor is locking up when it engages. Does the belt squeel or anything before it shuts off? Or does it shut off instantly, as soon as you flip the switch to on?

If the ac is on and the car is sitting there it will surge some below the normal idle and then die. If I keep my foot slightly on the gas it keeps running.

Well then it sounds like your A/C is causeing a strain on your engine. Probably due to a worn out stock compressor. But, does your A/C blow cold when the car is trying to die? Does it blow cold at all? I'm no A/C expert but I'd say you need to replace your compressor and probably have to replace your dryer too if you want a warranty (which you always want when working with A/C).

the compressor is good, the ac blows cold when I am driving and give the engine no problem

It's not the compressor. Your compressor is causing strain on the engine's electrical system for some reason. What are the volts at when the AC is on comparied to off? Are you running underdrive pulleys?