A/C vents seems to shut after awhile
I've got a '96 Olds LS with the manual climate controls.
When I'm cruising down the highway getting my 30.5 mpg with the air on, sometimes the vents seem to close, and no air some out anywhere, and just barely out of the vents, so the interior starts to get warm. I've figured out that if I shut off the a/c (it'* a seperate button on mine) in a few minutes, the air starts flowing full force out of the vents, and I can turn the a/c back on. On a long trip, I have to repeat this little procedure throughout the day.
It'* almost like the flap closes inside the system.
It only happens in the summer running the a/c.
Some have suggested a vacuum leak, but I don't know. I'm wondering if the coil is freezing up, and turning off the a/c lets it thaw the ice off and flow air through it again.
What'* weird is I use to have an '84 Olds 88 (rwd) that did the exact same thing, and i had to move the lever to vent and in a few minutes air would start flowing again, then I could put it back on a/c for awhile.
1996 Olds LS, 198,900 miles: RIP...