Chrysler Repair: Chrysler Imperial air distribution control, vacuum lines, vacuum line

Question
QUESTION: Hello Roland, I have a 1990 Chrysler Imperial. The problem I have is the air conditioning and heater will not come out of the front vents. If you select any other outlet (floor, defrost) it switches fine. I am assuming there is a motor that isn't moving properly. If you could please tell me what you think this is and where this part would be located it would be greatly appreciated.

Thanks for your time

ANSWER: Hi Tyler,
I believe that still in '90 the air distribution doors are operated via engine vacuum which is supplied by a narrow plastic vacuum line that branches off of the power brake vacuum line connector at the vacuum canister under the hood and goes through the firewall about midline (in line with the controls in the cabin. That vacuum line can be disconnected of cracked such that the vacuum supply to operate the air doors is disabled. So check that possibility first and let me know if that is not the reason and you may have to check the vacuum lines that are under the dash that are variously connected as requested.
Roland
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---------- FOLLOW-UP ----------

QUESTION: Hello again Roland, the heater/air fan switch for this car is digital automatic, and the brakes are abs - so the lines coming off the brakes are different. Does the actuator have anything to do with this issue, there are vacuum lines connected to that pce. You can hear switching under the dash when you press the buttons, there is just no air coming off the front vents at all. I have checked the vacuum lines but they all seem ok. I did have this same issue on 2 other new yorkers from 1989 with the same ATC control, but never found out the problem. Sorry to bother you, I just didn't want to have to disassemble the dash area unless it was necessary.

Thanks again

Answer
Hi Tyler
The ATC in the '90 is the same as '89, for which I have the manual. There are a number of tests and self-diagnostics that will help you sort this out.  I can xerox copy the 12 pages that describe the system and postal mail them to you. If you would send back four 44-cent stamps after you get them, that would be appreciated. Let me know a postal mailing address if you want the pages.
Roland
PS Please 'rate' my answer.