Air Conditioning

I am haveing a bit of trouble with the AC. When I turn the AC on it will start to get cold and once it gets to the proper cold temp it shuts off, than about every 10 to 20 seconds the ac will trun back on for another 10 to 20 seconds but the air coming out of the vents isn't very cold anymore and rob the engine of a lot of power.
I bought a pressure gauge and the coolent levels are ok.
I did notice where the compresor is, running off of the same wiring harness next to it is a bare wire that looks like it had been pulled off of something. I am not sure if this may be the cause for the intermitentness of it or not. I will have to trace it
Any feed back would be great.
2000 Rodeo AT 3.2L 125K

it turns out the problem was the ac system was way over charged. Damn that shop. I bought a gauge and was able to "bleed" it out of the system... We finally have our AC back just in time for the hot weather and the car doesn't run nearly as hard as before...