Cadillac Repair: Air conditioning, plastic vacuum, vacuum line

Question
QUESTION: Tom,my blend air door is not operating. The air comes on then goes straight to Defrost. This just started two days ago. At first it would switch back but now it will not. ANY help?

ANSWER: YEAR and MODEL of vehicle ??????????????

---------- FOLLOW-UP ----------

QUESTION: I'm sorry. It is 1997 Cadillac Sedan DeVille.

Answer
Has anyone been working on the car in the engine compartment or with the dash ?.

In most cases the fault is a loss of vacuum to the AC/Heater programmer.

Look in the engine compartment for a small black plastic vacuum line , May look like a wire but is much shinier than a wire looks, that goes thru the firewall and ino the engine compartment and make sure that it has vacuum in the line with the engine running.

Or it could be a faulty AC/HEATER PROGRAMMER or stuck AC/defrost actuator or door.

I can provide pictures and test procedures to you if you E-mail me at: onlineautohelp@msn.com