bimmerc90

I am aware the center vents on the W124 only blow cool air but mine do not blow any air ever. Does only air conditioned air come out of them? I'm a little confused on their function. It also seems like no air comes out of the under seat vents blowing toward back passenger. Could this be the vacuum unit behind the climate control 'brain'?

Saijin_Naib

Or blower motor.

ZaxW126

Hello, bimmerc90. What usually occurs is the vacuum actuators behind the dash go bad. They have a rubber diaphragm that over time splits and leaks, causing the symptom you describe. I have replaced many of them. The recirculate and center vent shut-off actuators require removal of the dash pad to replace. I have done many of these over the years. The labor time is roughly six to eight hours to replace all of them while you're in there.

madmaxbenz

I had this exact same problem and the shop wanted $2000 to fix it. It is correct that the dash has to be removed and then then the vacuum pods replaced. If, however, you are broke like I am, there is a cheap way to fix it. There is a baffle that closes when the heater is on and opens when its AC. If you can remove this baffle, then there will always be air blowing out of the center vents. Removing the baffle will lose the temperature selectivity of hot vs. cold, but living in South Texas, I couldn't handle not having the AC out of the center two vents; it was worth it for me. If you remove the vent assembly, you can reach your hand in and push your fingers down and feel the baffle open and close. There is a metal push rod that comes up from underneath the baffle causing it to open and close. Disconnect this linkage, remove that baffle, and the problem is solved! Also, if you're a handy mechanic, you can keep the center roll wheel in place and have a manual baffle which will let you keep the selectivity for the temperature. I was not good enough to do this, but I'm sure it's possible. Good luck!

ZaxW126

As a trained professional, we fix cars the right way, which is the "Mercedes way". Yes, you can undo the linkage rod, as described above for a "quick fix". No problem, if you have the skills. -Z

X03

If you do the 'quick fix' and remove the metal rod/baffle, at what temperature is it set at then? If I set it to cold before removing it, will it just stay at the cold setting?

madmaxbenz

Removing the baffle will cause air to always blow out of the center two vents at whatever temperature you choose. The heating and cooling system was originally set up so that cold air blows out of the two sides and center and warm air blows out of the two sides and footwells. The default position for the center vent is closed, and a vacuum has to open it. When that wears out, it can no longer act on the rod to open the baffle. Disconnecting the rod and removing the baffle will allow air to always blow out of the middle two vents, like the AC should. You will lose some air flow out of the foot wells when running the heater, but I NEEDED that AC. It gets hot here in Texas. If you have the $2k lying around, I recommend getting it fixed professionally. I'm putting myself through med school and couldn't afford it

X03

pfft... thats totally fine. I dont even care about the footwell vents lol

X03

btw, do you know how to just remove the center vent w/out removing the whole dash? I found these tutorials, but they seem to be replacing all the pods than trying to just remove the baffle

http://www.peachparts.com/Wikka/DoItYourSelf

Floobydust

The center vent is relatively easy:

1. If you have a passenger airbag car, remove the airbag assembly by removing the single 10 mm bolt. That bolt is accessed through a hole in the bottom of the front of the dash using a 6" or longer socket extension. If you lay on the passenger footwell floor, you can see the hole. The bolt sits vertically and is about 8" long. If you have non airbag car, open the glove box.

2. Remove the black phillips screw that attaches into the right side of the center vent louver assembly.

3. Use a flashlight and look into the area right behind the manual flow adjusting wheel. You will see an allen head bolt (it's small, maybe 2 mm). Unscrew this bolt - this will take several turns. The bolt will not come out, but unscrewing it will disconnect the wheel from the flap assembly.

4. Use the flashlight to locate the small metal clips that are located in the corners and at the back inside edge of the louver assembly. Carefully lift the tabs with a small screw driver so you can pry them loose.

5. The center vent louver assembly will now pull out of the dash.

X03

perfect! thanks to both of you guys, my center vents are blowing nice and cold now

khorrassany

I have the same issue would like to know which soltuion you took ? Did the same issue happen again afterwards?

Trevor Hadley

Would the aircon have anything to do with this problem? i know about the rubber diaphragm splitting but would the aircon over rule the air vents whan in use .