Cadillac Repair: A/C Air Flow, cadillac deville concours, vacuum leak

Question
I have a 93' Cadillac Deville Concours with a V8 32 Valve 4.6L Northstar, Vin #1G6KF52Y5RU202879.
The air comes out the defrost and not the front vents or the back seat vents, sometimes when I turn on the A/c it will start to come out the front vents but only for about 2 or 3 minites then goes back to coming out the defrost vent. Could this be the air door motor? If not could you help me and could you tell me where to find the air door motor and how to replace it? I have done most all my own automotive repairs. My email is: Rlaredneck@bellsouth.net.

Thanks Kindly,
Rocky Berry

Answer
In most cases this is caused by a vacuum leak.

locate the vacuum line that goes thru the firewall from the engine compartment into the inside of the vehicle. It is most likely a small black plastic tube. Back track it into the engine compartment and look for a loose or broken vaccum line.