heat ac control. cable hook up at?

Hello I recently bought a replacement heat/ac unit for my 91 GT but I'm having trouble installing it.

I dont know where the blue cable gets hooked up at. Is there a picture of it or can anyone tell me where is gets hooked up at?

This is what it looks like.

http://img379.imageshack.us/img379/3351/0808081624ue2.jpg

Assume the blue cable goes to the heater valve. Find where the coolant hose goes into the firewall, the valve may be there.

Assume the blue cable goes to the heater valve. Find where the coolant hose goes into the firewall, the valve may be there.

There are two cables the brown one is for heat that controls the coolant flow. I thought that the blue one controled the AC flow?

Its my AC that is not working.