1995 Ford Contour A/C problem

My question concerns a 1995 v-6 Ford Contour 100k mi.

My a/c is blowing on defrost only. I've checked for a vaccum line leak to the dashpot(s) located under the dash and can't find one. I can divert the air to the floor vents by manually activating the dashpot to the left of the center console (the one nearest the gas pedal), but nothing happens if I try to manually activate the one directly behind the car stereo. I'm not a mechanic or an expert by far, I've only gotten this far by doing some amateur inspection.

So I guess I would ask, could the a/c distribution switch itself be bad (looks ok from the outside) or is there something else that I could look for. I can't find a diagram anywhere of all of the vaccum lines, so I don't know where else to look for possible leaks.

I don't know if it will be relevant or not, but while looking I also discovered that the wiring harness plug to the fan blower speed control switch had gotten hot and charred part of the plug at some point. I'm going to replace the burnt plug and switch. Not sure if this could have done damage to anything else with the system?

Any help would be much appreciated.