I think I am missing a short harness of some sort. I found this description on the web.
The control harness is about one foot long, and separates into two plugs which connect to the compressor switch and the fan speed switch. Earlier Firebirds were wired so that Max A/C always put the fan on high. At some point (probably 1980), this connection was eliminated. The little extra plug connects to the power supply from the I.P. harness. The early harness is shown on the left, and the later harness on the right.
Anyone have one?