That's all it's got - 1 wire. Problem is, none of the original underhood harness remains from the previous owner.
Also, I've looked on the factory AC controls and I see nothing that seems to tie into the compressor, just blower motor wires. Perhaps the AC is controlled off one of those?????
on my car there was one lone female bullet type connector coming out of the firewall below all of the other harnesses and that was the compressor wire, i'd be willing to bet your's is similar
well if you can post a pic of the drivers side firewall area to about the middle of the firewall i can try to help you pick out which one it is, provided it's still there