You have four cables, three that hook up to the air,def. and temp. contols switch in cab right.
Two cables hook up inside by the heater assembley under your dash, right.
Two go through the fire wall, one should hook up to the inline controler for your heater hose and the other hooks up to the outside vent by the blower unit under the hood,to draw fresh air up to the heater core to be relased into the cab, least that is how mine are hooked up. Hope that is what you are looking for, if not maybe some one eles can add to it.
You are very right Heat is great when it is -40 below and the Saskatchewan wind drops it down to -50 with no heater in the truck, it is like driving in a frezzer, LOL.
