Weird Air Vent Problem
 

Okay, this is a strange one. I am thinking vacuum leak somewhere.


'90 300SE. A/C runs decent, having been retrofitted to 134A.


With the A/C on, the airflow will come out of the center vents for a little while (usually). Then, without me doing anything to the controls, it will route all the air through the defrost slots.

If I put the system on EC (economy, AC compressor off), the air will come out through the center again. If I switch it back to A/C, sometimes the air will continue to come through the center vents, sometimes it will switch immediately to defrost vents. Sometimes it will run on center vents for a good long while and then just spontaneously switch to defroster again.

One thing that seems to be a pattern is that it will often switch to defroster under acceleration. This is why me thinks this is a vacuum issue.


Question is: Where do I look? What innumerable assemblies have to be removed to get to it?



Thanks much!!


Jamie

Vacuum pod test block
 

# 59 is the vacuum pod test block (You can plug in your mighty vac to each
pod's circuit and test for leaks) I think you have to pull out the glove box
liner to access it.Be careful with the glove box light!

I was afraid it meant diggin in the dash. Thanks for posting the diagram. I will try to to a leakdown test on it tonight.


Thanks!