c280 -- Where are vacuum servos and heater valve located?
 

I've posted in vain in the following thread but got no answers -- http://www.peachparts.com/shopforum/tech-help/17822-ac-vents-center-vs-side-vents.html

My 94 C280 is having the hot air from some vents (usually side vents, sometimes foot vent), cold air from others (mainly middle) problem. It has been indicated that this is typically a vacuum issue but sometimes could be a heater valve.

I do not know where to begin on this. Could someone give me a link with diagrams or give me some pointers?

Side issue -- had my crank sensor replaced a couple of weeks ago. Ever since -- the transmission shifts have been VERY harsh. I'm told that likely some vacuum line was disconnected during the repair. The A/C vent issue started soon after that, but not immediately after that. Is it possible that these are related?

Thanks very much in advance of any help you can give.

do a search for "duovalve" on the heater valve and you will find some good info. the duovalve is located in the rear left (passenger side) of the engine compartment.

Have a look here for diagrams, just search the list for your car and work your way in to what you need.http://www.detali.ru/cat/oem_mb0.asp?TP=1.
The problem you have with harsh shifts sounds familiar, mine was caused by the vacuum pipe (white) from the inlet manifold to the gearbox being disconnected at the gearbox end ,it passes close to the TDC sensor and connects at the driver side towards the front of the box, bit of a pig to reconnect but worth the effort. It may be that the loss of vacuum if this pipe is off is also responsible for your other problem,I don't know.
Hope this helps, Geo.:) :) :)

I was having the same problem with my '94 C280. Hot air out of the side vents and cool air out of the center vents. My fix was replacing the "duovalve" or dual valve. If you go to any website that sales parts and look it up you will see a photo. It is located under the cover near the firewall on the passenger side of the engine bay. A fairly easy do-it-yourself project.