a/c question

96 bronco, A/C redirects to defrost and floor vents when accelerating and all the time in Max air, I know it's a vacuum issue and have found only one valve/vacuum part in parts manuals for it so I figure that must be it. Does anybody have any idea where this valve/vacuum is located and the best way to go about changing it? I can't find any info on how to do the repair.

Welcome to AF!

The blend door actuator is vacuum controlled. If you have a vacuum leak the door defaults to the defroster setting. Set the A/C on a normal setting with the air coming out of the dash vents. Starting at the vacuum source pinch off the hoses one at a time. When the A/C goes to the defroster vents this is the line you want to trace for leaks. If a vacuum hose was off completely the A/C would go through the defroster vents all the time. Because the A/C goes to the default under acceleration is an indicator that maybe the vacuum canister is leaking. It is supposed to hold enough vacuum to operate the system under a load. In addition it could be a leaky hose or a hole in the vacuum motor diaphragm.

Thank you Davescort97, I'll start tearing into it today until it gets to hot to work on it, no shade tree for this (not so) mechanic -al.