300E Center Vent Problem
 

The center vents on my 1988 300E is not functioning. It's closed permanently, and it's lever does not open nor close the air openings so that air can flow.

I need to know a way to open up the center vent pasage way/fix the lever problem for the center vent.

Also, the A/C compressor seems always on even when the climate control is set to off or hot. I can feel the a/c cooled air flowing through the two side vents.

Thank you.

Is the thumbwheel connected to the vent flap? If not, you can try reinserting the connecting rod to the flap with a small allen key (i forget what size, maybe 5mm). It doesn't screw in all the way, maybe about a third of the way - only until you can fully close and open it without too much effort.

If the thumbwheel IS connected to the vent flap, then the vacuum pods controlling the center vent flow may be busted. Fixing this is much more involved, and involves pulling out the dashboard..

Thanks for your help. Looks like I need to pull the dash assembly.

maybe you don't need to
 

From your description it sounds plausible that the dash control unit may be faulty. Try looking at that first before going for the vacum servos behind the dash (that is the long expensive job). If you eventually need to change the servos, replace them all, and also consider changing the evaporator (you don't want to go in there twice).

goog luck

Actually, in thinking about it more, Champa may be right. It could also be the vacuum distribution block. A better way to check the vacuum pods (all of them) without pulling the dash is to pull the glove box. That will give you access to vacuum distribution box, which is attached to the heater box. Slowly pull off the lines one at a time and attach it to a hand-held vacuum pump. They should hold a vacuum, if not *then* the pod may be busted.

Sorry, missed that critical diagnosis step!