I have a 97 TA with 54k mi on it,stock exept for a flowmaster. When I turn on my AC or heat the foot vents and the little ones in the corner where the a pilliar runs in to the dash work but not the big circular vents that go across the dash. I hope that makes sense. I checked every thing I could think of nothing is diconnected that I can see.

Thanks in advance
Jay

 

Sounds like you have a vacuum leak going to the a/c heater control head and its not allowing the air to be directed in the vents you want it to.

 

I would bet a large sum of money its the A/C check valve.

It is located near the firewall on the left side of your car if you stand in front of it. It looks like a little T, that will be either black or white plastic. It has 3 lines running into it, one on the top, one on the side, and one one the bottome. If it looses pressure your vents will blow from the default position defrost. If it gets a leak you vents will not switch properly and may erractically blow from different vents. The part is about 4 bucks from the dealer and takes 12 seconds to replace. I have been through about 6 of these cause they keep on cracking.