Heater valve

Is it just my jeep, or does the heater valve open even when the A/c is on. The line going to it gets vaccum all the time except when the controls are off. Any thoughts on putting a switch in to help A/C performance
Dustin

What year??

On the early slide-controls the valve is supposed to close when you're slide is set to "COLD" -- the issue there is that there is a cable operated door that's also operated by the "COLD/HOT" slide -- if that cable is out of adjustment far enough so that the slide doesn't hit the left(cold) edge of the slide, then the vacuum control switch doesn't even get a cule to shut the heat valve...

For those models, the offending cable runs from the slide to the airbox in the passenger's footwell - a little contorting is all it'll take to access the adjustment (it's on the airbox end of the cable)...