View Full Version : 1969 DeVille - Vent Operation - Automatic Climate Control

04-19-11, 09:16 PM
According to the owners manual, when the VENT setting is selected on a car with the Automatic Climate control option, outside air is discharged through the "three dual air conditioning outlets" which i beleive are the dash outlets.

In my car, when I select VENT, seering hot air comes out the heater outlets at the floor level. That doesn't seem right....

When I select AUTO (LO or HI), seering hot air comes out the heater outlets at the floor level. If i switch to FOG or ICE, hot air comes out the windshield vents. In the interest of full disclosure, the AC is totally disengaged and there are no belts going around the AC compressor in my car.

It would be nice to know why the VENT setting doesn't discharge fresh air out the dash, but rather, full heat out the bottom?

04-19-11, 09:24 PM
I'm not familiar with your vintage of Climate Control, but they probably used engine vacuum to change where the air came out (that is how things operate on my '89). There should be a vacuum canister mounted somewhere on the firewall that goes to the blend doors. If you haven't done so already, now would probably be a good time to replace all of your vacuum lines and make sure emissions routing is factory correct.

04-19-11, 09:39 PM
Since your defroster vents are working, i would suspect that the ac door vacuum actuator is ruptured or stuck. It appears that you are getting vacuum to the ac control components. Also it could be a broken/ cracked hose somewhere along the way to the actuator.
Hope this helps,

04-20-11, 10:00 AM
Interesting... I'll look through the shop manual for the components you both listed (ac door vacuum actuator) and start there.


04-20-11, 01:35 PM
The climate controls are controlled by engine vacuum. Check vacuum lines first and be sure there is no obstruction in the doors movements. If those components are ok, then probably the A/C Heater ATC Power Servo (I think itīs the same than the ac door vacuum actuator) doesnīt work properly. It controls which part of the circuit must be closed or opened according to the dash control position. Iīve heard that itīs usual this component fails. Iīve changed mine; I got it here: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=360329273926&viewitem=&sspagename=ADME%3AB%3AEOIBSA%3AES%3A1123