A/C center vent problem
 

Hello group,
First time poster, long time reader...

I have a peculiar problem with a used E320 we bought about a month ago... The AC blows nice and cold from both sides but with one peculiarity... It doesnt blow from the center vent. It blows cold from the defroster and causes condensation on the windshield when it's nice and humid out though! Also, when I hit the rear headrest release button on the dashboard, it seems to open the channel to the center vent openings, and then automaticaly closes after about 15 seconds... Has anybody else encountered this problem? If so, is there a fix to it? I changed the cabin filters thanks to a post with illustrations (thanks to the tech guy from Atlanta) so its not that. I have not changed the activated carbon filter, but do not suspect this as a cause... any help would be appreciated. Other than that, as a former BMW loyalist, I am thoroughly impressed with the quality and craftmanship on my new toy, and love the way it feels on the road. Just put a new set of bridgestone turanza LS-h's on it and WOW what an automobile!!!

Thanks for any feedback

RE: A/C center vent problem
 

These 2 systems use vacuum to operate them. It may be that you have a vacuum leak somewhere in the system. Each vent has a vacuum diaphram which opens and closes it. Sometimes these diaphrams leak.

RE: A/C center vent problem
 

OK, sounds reasonable, so where would one begin their search for a vaccuum leak?
And what would the rear headrest release button have to do with the center vent operation???
Futher, I checked the different vent setting combinations... (top, middle, bottom...) and they cant be changed from the climate controll panel on the dashboard. Whats up with that?
Also, since the car is a 96 and no longer under warranty, would a problem like this fall under manufacturers defect, as I cant imagine how something like this would occur otherwise.

I just want the car to work as it's supposed to, you know? I have time and patience to remidy problems like this if I just knew where to start...


Thank again

RE: A/C center vent problem
 

This problem will not fall under a manufacturers defect.

The best thing to do is park somewhere quite and start the car. Listen for a hiss. You might be lucky enough to find it this way if the leak is big enough. Also check vacuum connections under the bonnet.

RE: A/C center vent problem
 

ok, for anyone who encounters this problem...
the cause of the rear headrests not staying locked in the upright position and the center vent being inoperable... in fact, the air flow director of the climate control unit was completely ineffective was....

the white vacuum hoses to the pneumatic control system under the back seat were reversed!

just switching them put the planets back into allignment. now the door locks snap up and down, the headrests stay upright until released from the dashboard console, and the air comes out of the corresponding vents as directed!!!!

oh, happy day!


had a mb mechanic hook me up to the computer and checked all my systems software, error codes and such.. it didnt come up. then he switched the hoses just as a guess and lo and behold, that was all it was! how (*%&@(*%$'in lucky was I???

He says the car is tip-top... nothing needs adjusting, no leakes no problems at all.

I'm a happy dog.