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Old 06-13-2003, 11:06 AM
Registered User
Join Date: Mar 2003
Location: Convent Station, NJ
Posts: 755
380sl center vents not working. Yes, this is a common problem

After operating the A/C I realized the center vents do not function on my 1985 380sl.

Did a search on this subject and found it to be a common problem. Unfortunately, the info is mostly for other models.
What I have learned is the following:

- The vents are operated by vacuum via an actuator.

- The defrost vents and center dash vents may be related in operation...each with there own actuator.

- The actuators can be labor intensive to get to. But I don't know where they are on the 380sl.

- Actuators can be expensive, however, if the diaphram is the culprit thre are sources to buy this part seperately.

- Problem may also be vacuum supply to the actuator(s).


-Can anyone direct me to the location of the center vent and/or defrost actuator and perhaps an idea of how to get to it?

-Any other obvious components to consider?

-Is there a vacuum diagram available on the net?

Any and all help is appreciated!

'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac
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Old 06-15-2003, 10:03 PM
Registered User
Join Date: Feb 2003
Location: Texas Hill Country
Posts: 6
My suggestion after resolving exact same complaint on 87SDL.

1. Replace every questionable rubber or silicone vacuum connection between a hard plastic hose and a vacum device. Even using MB parts a number of 2" connectors will not cost much.
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Old 06-15-2003, 10:24 PM
Registered User
Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Two causes, usually -- a bad climate control fuse (low speed blower only, heat only out the defrost no matter what button you push) or a vac leak.

First thing to check is the condition of the vac lines in the engine compartment. The green hard plastic line is the one for the climate control. If it is bad, you get air out the defrost, floor, or side vents only, no center vents.

The system has to hold vac. Best thing to do is head to the auto parts store or Sears and buy and MitiVac hand pump. Nice little gadget, you can then hook it up to the green line and pump away. If the center vents now work, hook up to the other engine end and find out why you don't have vac.

Most common cause is a dead rubber connector. These can be replaced by the MB part, or by simple vac line (1/8") from the autoparts store.

Occasionally a hard plastic line will break -- they get brittle with age -- you can splice it with vac line.

If you have good vac on the engine side, you will need to go hunting under the dash for the vac servos. Some are accesable on the W107, I think, but I'm not sure. You may have to do some dign ito the guts of the dash. If so, I'd replace all of them, or at least the diaphrams, to avoid a repetition of a long job later.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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