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Old 07-29-2002, 02:55 PM
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Smile Center Vents

Can anyone tell me if the center vents on a '86 560SL are susposed to blow a/c air out of them? The only thing they do is blow warm air when the heater is on. If it was made to blow the a/c out of them what is wrong and what is the fix? Thanks to all...
Larry '86 560 SL
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Old 07-30-2002, 10:14 PM
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Join Date: Feb 2002
Location: Alexandria, VA
Posts: 326
My understanding is that the center vent is suppossed to shut off during A/C
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Old 07-31-2002, 12:36 PM
Mark Herzig's Avatar
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the center vents do not blow when the heat is on but do blow cold with the ac on.
Mark Herzig
1995 E300D 153K
1985 300D 142K (sold)
1979 450SL 122 miles (sold)
1992 500E 127K (sold)
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Old 07-31-2002, 10:24 PM
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Location: churchville MD
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center vents

Hi guys I am having the same problem.When AC is on cold air only comes through two outer vents when in suggested mode.When in multi mode AC comes from two outer vents plus two center vents. Can anyone tell me how a properly operating system operates on a 1987SL ????
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Old 08-01-2002, 05:05 PM
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Posts: 51
Center Vents

I have both an 87 and 88 and the center vents definitely are used to blow cold air when the AC is on. If they don't, you have a problem with one of the vacuum valves in the dash that control air flow. This is a common problem with the 560SL--and fairly expensive to fix. Do a search and you should find many threads on this. As I understand it, depending on what valve is bad, the dash likely has to be removed. Proper functioning of the center vents is one of the key things to look for if you are considering the purchase of a 560SL, since the repair is non-trivial. Frankly, I would just drive it--it won't hurt a thing, but it definitely is not working as designed.
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Old 08-02-2002, 11:04 PM
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Location: Colorado, USA
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Center vents


Think vacuum! More than likely the vacuum actuators that control the center vents have gone kaput. If the air is being diverted to the defroster outlets then the system is in the failure default mode. The most common problem with a car of this age is a bad diaphram in one or more of the vacuum actuators. Please note that you do not need to replace the the entire actuator, unless it is broken(rare), only the rubber diaphrams. These diaphrams are unavailable through Mercedes-Benz, but can be found aftermarket for about $5.00 each. The vacuum actuators are controled by crossover valves. [I'de have to look up the location of the crossover valve on a W107, but on a 126 they're inside the center console, behind the radio.]
These crossover valves are electrically actuated by the temperature control box. I believe this box is found mounted behind the glove box.
This is not a terrible job,but it's labor intensive. Parts shouldn't be that much if it's just the diaphrams. You should probably have a manual to help sort out the system and the parts locations though.

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Old 08-03-2002, 11:07 AM
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Join Date: Jul 2002
Location: churchville MD
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center vents

Thanks Very Much Guys. Any tools literature I should have on hand before I start the job. When I push multi AC button air comes from center vents but fogs windshield.When I push the normal button AC comes from center vents for about 15 seconds then slowly stops.
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Old 08-05-2002, 01:46 PM
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Location: Alexandria, VA
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My center vents are on with the A/C on as well. Does this mean I have the same problem? Thanks.
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