What causes the ac to only blow out the defrost and floor no matter what postion it is set for on a 2001 cadilac devill

SOURCE: AC blows through defrost and floor vents instead of ac vents

You have a vacuum leak in the system that controls the vent doors. First check for cracks at the vacuum reservoir, then check the various vacuum hoses and vacuum motors for a leak.
Charlie

SOURCE: change starter in 2001 cad devile

The starter on that engine is mounted between the cylinder heads under the intake manifold. You will need a set of injector O-rings and an intake manifold gasket set to do the job. It is not really hard to do, but a bunch of stuff has to come loose to get the manifold off.
HINT: The gasket surfaces for the intake manifold are very easy to clean up in preparation of re-installing the manifold if you use some rags and carburetor cleaner.

Stephen

• 21873 Answers
• Posted on Aug 24, 2012

SOURCE: my ac blows out defroster and floor vents

Could be a blend door problem, or the ac controller.