AC problem
 

i have this weird problem with my AC, if i turn the AC fan on 1,2 or 3 i get hot air, but if i turn it stright to 4, i get cold air. but the cold air only lasts for 2 or 3 minutes. i can hear the compressor come on and off about 2 or 3 times a minute and then it just quits working. and thats not the only weird thing, i found a green wire in my glove box are that has to do something with the AC, if i move that wire, the compressor kicks in but not for long. help guys its Texas and its HOT.