Air vents stop blowing air at higher RPMs.

My vents will stop blowing air above ~2200RPM. It will do this regardless of fan speed and temperature settings. I can still hear the fan working, I am just not getting air from the vents.

I assume the vents are vacuum actuated and that is where my problem lies. Anybody have any experience with this problem?

2001 3.1L

The vents default to def/floor when the vacuum supply that controls them is lost. Under acceleration engine vacuum is very low, and will deplete fast if there's a leak, especially in the vac reservoir....

Check the lines to it and the ball itself...up inside the driver's side front fender.

PS the line to it is easy to pinch or break during battery replacement, if that was done recently...