AC compressor relay and Trinary switch wiring question

[kglowacky]

going thru the same process of getting my ac working. when I got my harness back from the rebuilder he left a wire on it saying AC. I called and asked why he left it on there because I said no to ac on the build. He said they made a mistake just ignore it. Now I am wondering if he didn't do me a favor by leaving it. My question is is this wire connect to 12v or a ground or does it connect to the compressor and the compressor tell the ECM to increase rpms to handle the extra load. or connect to a relay terminal. Assume it is pin#17.