Cadillac Repair: 1999 Deville Concours AC/Heat, diagnostic scanner, defrosters

Question
Dear Tom sometimes when i set the heat or defrosters to come on the left side will put out heat and the right side will put out cold when this happens i shut it off and i set it back to 60degress and then i hear a noise the moving vent but sounding squeaky and if i move the climate control one degree at a time it will work again sometimes rfor a little while sometimes the rest of the day it was said some A/C systems are electric and some vacuumed can you help

Answer
There are 2 damper door actuators, One for the drivers side and one for the passengers side as well as a vent controller for each side. Most likely the damper door actuator on the passengers side is faulty and due to it's location way up under the dash, A diagnostic scanner that has the ability to test the actuators needs to be utilized to determine fault.