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82 240D; 83 300SD
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18 Posts
Discussion Starter · #1 ·
How do I manually turn the defrost vent off on a W126 300SD? Where is the defrost door at that I need to shut?[?]
 

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1991 300 SE
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18,534 Posts
I assume you have all defrost all the time. Unfortunately that’s a vacuum related problem. Somewhere in your vacuum system there’s a leak and you need to check all the vacuum lines for a broken or disconnected line.

As you’re in Florida you might want to disengage the defrost as we rarely have ice on the windshield. Remove the glove box compartment and to the left you’ll see the vent controls attached to the actuators by a short linkage. Unhook the linkage and manually close the defrost vent. You won’t be able to get the center vents to work but you can get the side vents to work by unhooking the linkage as well and leaving them open all the time. It’s far from a perfect fix but it will keep the frost off of the windscreen with the AC on and direct some cold air to the cabin via the side vents.
 

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82 240D; 83 300SD
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18 Posts
Discussion Starter · #4 ·
Thank you so much. That worked great. I still have air coming out of the center vents it just keeps ramdomly blowing high or low, but the side vents stay constant. Main thing is I no longer have the A/C fogging up the inside of my windshield.

Thanks again! [:D]
 

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1983 380SEL
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17 Posts
Is there a way to manually open the center vents? I understand this is vacuum related. By unhooking the linkage attached to an actuator, you can close (or open) the defrost vent. Correct? Is there someway to "manually" close or open the center vents?
 

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'89 420SEL, '93 300E and '07 Hyu Santa Fe
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567 Posts
Is there a way to manually open the center vents? I understand this is vacuum related. By unhooking the linkage attached to an actuator, you can close (or open) the defrost vent. Correct? Is there someway to "manually" close or open the center vents?
Exact question.

My defrost vent element is busted and I can't take it off from its base. When i closed all vents and manually closed defrost, very light blow came out of center vents but most air tried to blow through driver side upper vent because there was no other vent open.
If only manually closed defrost and let other vents open, flow works perfectly but center vents won't work.
Is defrost element busted and center vent not working related? Center vent element looks good in shape from outside, don't know how rubber inside is. Hopefully intact. Btw it's 1989 420SEL
 
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