I redid all my heater cables and controls about a year ago, so I'll do my best to remember. The cable with the white tab connects from the top left peg of the control box to a fresh air door on the driver's side (top left of the whole air box) AND then continues to the fresh air door on the passenger side. This double cable is probably why the diagram has 4 cables when there is only three. You'll notice this cable has a threaded portion. This is so you can adjust it so that both fresh air doors open and close completely and align with the correct spot on the control box. The second cable hooks up to the top right peg of the control box and leads to the heat/defrost door. This is a right above the foot heater outlet. The final cable goes from the bottom of the control box to the blend door (above passenger foot-well, left of the passenger fresh air door). This controls how much air blows over the heater core. The vacuum fittings on the back of the control box are to control the vacuum motor at the top of the inlet duct. This shuts of the flow of air when you have the switch in the off position. Make sure that the little tab on the vacuum switch is depressed when the heater control is in the "off" position, but it is NOT depressed when you move it anywhere else (defrost, heater, vent). I had to bend the metal tab on the control box a bit to get it to sit just right. Same deal with the leaf spring on the right side of the control box. This is a switch that turns the blower motor OFF when the control is in "off" or "vent". The leaf spring switch should be pushed in at this time. It should click out when you have the control in "heat" or "defrost".
Final note. The little plastic tabs on the control box that hold the cable ends are old. On mine they either lost tension and the cables would slip off, or the tabs would just break from brittleness. I drilled these out and used a small bolt, nut, and washers on each side to hold the cable end in place. Haven't had any issues. Not a requirement. Just a suggestion.
