Vacuum / And Cold air return door MAX/AC
So I have been trying to fix this problem with my AC. There is a cold air return door behind the glove box that works off vacuum, It looks like the two main line come in just below the door it is a white and black tube the split a few times shortly after entering the inside of the truck they travel to the heater and ac selector **** on the dash and go to other places think there are a total of five that come from the selector and go to different locations the White Line goes back to the regulator for the cold air return door that should open when **** is on Max Ac . When my selector is placed on max ac the door moves but will not open there is not enough vacuum, I can pull vacuum with pump and door opens just fine. So it is not the regulator I don't think, I replaced the selector switch and still does not correct the problem.
Anyone have any suggestions as to what to try next?
Any one know where this vacuum come from before it enters the through the fire wall?
How much vacuum should it take to draw the regulator down to open the door?
There has to be simple fix here put vacuum on it from another line and door opens right up
. Are there no ford techs on here that can help point me in the right direction?