Py passenger foot vent works propery, with the vent door opening and closing when the climate control tells it too. My drivers does not and stays shut. I just spent and hour our so peeking in my drivers foot vent and staring at the back side of my passenger vent trying to determine what makes these doors open and close. I see nothing attached to them to swing them open or shut. I was hoping it was just some sort of push rod or something and I could just re-attach the one on my drivers side, but no luck.

So what is it that actually, mechanically opens and shuts these vent doors?

Thanks

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1983 300SD

The flaps are positioned by vacuum actuators which are operated by electrically controlled valves.

But I was under the impression that there is only one actuator that opens both vents. So if one works, the other should.

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1983 300SD

That is correct.

So if one works and the other does not, that means the the accuator is working, but for some reason, the drivers vent is not connected to it or something, since it is not working. How does the accuator connect to the vent to make it open and close?

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1983 300SD

Well, I guess I just stick wedge in there to jam the vent open. I'd rather have air on my feet all the time then never.

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1983 300SD

There is a separate linkage for each flap. The fact that one flap works would seem to exclude the actuator as the problem. That leaves the linkage between the actuator and flap as the prime suspect.

Where could I find this linkage? My super sleuthing with a flashlight and jamming my arm in there have found nothing.

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1983 300SD

I have a 300D, so I don't know the details of the SD except for what I see in the schematics. On the D, the linkages are pretty visible. It's a plastic rod that connects to a bellcrank that rotates the flap. The SD schematic shows a single acuator with a linkage to each footwell flap. The actuator should be springloaded to the closed position and opened when vacuum is applied. The flaps are positioned either fully open or fully closed; there is no intermediate position.

If you try to move the inoperative flap, does it move freely or is there resistance?

The inoperative flap moves freely and if I don't push it all the way open (basically jamming it open) it will close. The opperative flap opens with strong resistance. So much so, that I don't really want to try to hard.

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1983 300SD

Has anybody messed with their foot vents on the SD? I really want to figure this out before I put everything back together again.

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1983 300SD

OK, after alot of cramming my head under my dash and reaching up and pushing a lot of buttons to see what happens, the drivers side vent DOES work, it's just very very weak. It will only open half way very slowly, if I turn the fan on high, it will essentially shut. It's so weak, it really should be consisdered inoperative. Vacuum leak maybe? The passenger one is very strong.

I know everyboy is bored with this thread, and I'm bored dealing with it too. Sorry, I just want to see if I can fix this.

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1983 300SD

If it makes you feel any better, the SD does the exact same thing. The passenger footwell is very strong and the driver footwell is, essentially, shutdown.

My suspicion is that the driver's footwell vent has disengaged from the bellcrank in some fashion........so........it's just flopping in the breeze. The passenger footwell vent is properly connected to the vacuum pod and it's difficult to push the vent open because you must force the pod in the opposite direction.........not easy to do.

But, too many other eggs to fry right now..........so..........I'll let you fix it.

I will let you know if/when I do. If you beat me too it though, fill me in!

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1983 300SD