A/C is cold but dash vents are whimsical and take turns working properly--occasionally they work fine and then other times not. If I adjust the fan speed and turn the A/C switch off and on that sometimes that gets air flowing again. Everything is fine when I stop and re-start the car or start it first thing.

Thanks to previous BB help I replaced the black and white vacuum check valve on the intake manifold. That was not the only problem so I'm wondering if there are other vacuum valves under the dash that need attention? Are there diagrams available that show what controls the opening and closing of the dash vents, the defroster, etc.? Any other ideas?

I'm in the Sunbelt so I'll be using my A/C year round.

Thanks for your help.