I have a 1999 Alero that will only blow air out of the floor vents. No matter what setting the heater/ac is on, no air will flow out of the dash vents. I have been told to look for the vacuum lines that go through the firewall, but I am not able to locate them. If anyone knows the specific location of this line or has any other suggestions, I would greatly appreciate it.

well if u can find the main vacuum it should lead off there if not. usually most gm vehicles have a picture of the lines right when u open the hood in front of where the radiator is an the are colored and labeled if not check your owners manual or buy a chilton repair book they should have them at carquest or other parts stores.