A/C Issue - Vacuum?

The AC in my 2000 Dakota is acting up randomly. I noticed it one day when I had it on Max and the air got warm. After a couple minutes it cooled back down.

Then the other day I had it on normal blowing out the dash when the air stopped blowing. At first I thought maybe it had frozen up but then I noticed the air was coming out the defrost rather than the dash. After a minute or so it started blowing out the dash again.

Are the mixer doors operated by vacuum? I was thinking maybe there is a leak causing the doors to not operate properly. Is my thinking correct? Where should I start looking?



Thanks!!

They are vacuum operated. Vacuum is fed to the inside to the control head through a black plastic tube. There is a check valve in this line in the eng compartment so you either have a leak or the valve is bad.

Thanks!

Where on the firewall does the vacuum line run through?

Where the AC lines come through the firewall.