1989 Cadillac Sedan De Ville engine stalls when air is turned on...tries to take off when stopped at stoplight..sometimes dies while driving..

It sounds like the idle compensation circuit for the engine is dirty or faulty. Have your car checked at a shop. have them check the idle air motor for dirt or malfunction. It could be that it only needs to be cleaned or replaced.

The compensation circuit adjusts the idle/slow speed of the engine. The air conditioner puts a load on the engine and this circuit adjusts the engine speed to compensate. Also, when the car is cold this circuit adjusts the idle speed to prevent stalling and help the engine warm up faster. I hope this information helps you.