[Dandruff461]

Hello everyone. As stated i have a 1990 new yorker. The ac works just fine except either the actuator is going out or i have a leak in a vacuum line. Heres my situation. The air can blow out the dash but only if i have it on the lowest blower setting (hot or cold doesnt matter). But if you increase the blower speed you hear the doors go thud on the inside and it defaults to the floor / defrost. The only way to get it back is to shut off the car and start again. Whats your guys's opinions about this? Thanks for your time in advance

 

[Oklahoma Wolf]

Sounds like a vacuum leak somewhere, at any rate. 1990 was one year before they went to electric motors, so there will be a fair few vacuum lines to check out. There will be a supply line running from the engine to the power/vacuum module in the airbox located behind the glove box, and several coming out of it going to the various actuators.

First place I'd check is under the hood - the hard plastic lines Chrysler used back then love to get brittle and crack.

 

[ImperialCrown]

There was Semi-Automatic Temperature Control (SATC) and Automatic Temperature Control (ATC). You might be well-served by finding a Body Diagnostic Procedures book for AC/AY bodies that would cover Chrysler Climate Control systems. There may be a separate diagnostic book for ATC. Servo failure was fairly common.
These diagnostics may be later (1993) than yours and may not apply, but try to see if codes come up:

http://www.allpar.com/fix/codes-climate.html

 

[Dandruff461]

Ok so i checked the error code i got #2. Meaning the door didnt reach panel position. Thanks error code. I already knew that. I guess i wont be able to know till i get in there and search. Besides visual inspection, is there another way to tell if its a vacuum leak?

 

[ImperialCrown]

Getting a fault code is a good confirmation of the problem. For vacuum leaks, listen for hiss while the door is actuating? You may need to hang upside down under the dash with the doors closed and windows up for silence with a light for observation of the air door actuator/linkage movement.
I may have the student workbook somewhere that would explain diagnosis of the code and its possible causes.
It could be mechanical like a sticking mode air door? I have found pens and coins inside HVAC housings that have blocked door travel. Sometimes the rubber or foam sealing flap that surrounds the air door edges gets gummy or the adhesive fails and the piece falls into the path of travel. If there is external linkage, see if it is moving when actuated. If there is a potentiometer that measures door travel to confirm door position and report back to the controller that it moved, it may be giving false information?

 

[Dandruff461]

well ima go try to diagnose tomorow. maybe tonight if i feel up to it. im currently installing a new shower so ill post back when i have update.