Thanks, Broncojoe! Very nice post. I completed most of the same steps you did already, and looking at your pictures was like looking at my car - funny feeling. Anyway, the only thing that's different on mine is that when I block the opening of the black vacuum line going to the rear switch, my front vents still do not work. I actually tried that yesterday morning, following the same logic you just explained. I do not feel any vacuum, not on the ends going to the switch, not by the actuators (both front and back). All lines going to VCMs seem to have very good fitting connection. So my next step seemed to be measuring the pressure, however, as I said before, I do not have any testing equipment (unlike you) to say how many inches of vacuum I have and where. I went to AutoZone this morning and asked for it, and the guy said he has nothing like that, and recommended checking for cracked vacuum lines under the hood. This is where I get lost, broncojoe - I do not know what to look for and where. Obviously, replacing the rear switch did not fix my problem. Not feeling any vacuum with my finger, I am guessing not enough vacuum coming to either the front or the rear switch over the main black line.
I looked under the hood for any lose or missing connections - did not see any. I than came back to the car and looked at the black line again. At the clear plastic T - where the main black splits into 2, one going to front and one going to rear switch - I noticed some sort of green stuff inside. The same green gunk was on the front switch where the black line connects. So I stuck the wire inside it and it took me about 10 minutes to fish that green sticky gunk out. I got all of it out, but the system is still not working. So I am wondering at this point what that green stuff is, and is it inside that black line beyond the T. I followed the main black line, from the switch, through the dashboard, almost the glove compartment and than through the firewall into the engine compartment, where it terminated into a T with another red line (not sure what that one does) and into the black box. Did not see any crack. Not sure about the next step, let me know your thoughts. Thank you all! | 
