I have a 1989 420 SEL that blows my cool air of my air conditioner through my defrosters only. My MB dealership (Schumacher European) says that it's a common problem on the w126, but expensive to fix. About 1,000.00 $. Any suggestions?

It is a easy DIY job, you have 1 or more (up to 6) leaking vacuum actuators around the evaporator box. Cost should be no more than $200.00. There is probably a link in the archives at http://www.BuyMBparts.com ("]www.mbz.org[/url]. I have more Mercedes parts at lower prices than ANYONE. 27 years in Mercedes parts sales. 1-800-741-5252 or [url=")</P>


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I have a similar problem. When I have the heater on it blows ice cold air into the back seat through the vent in the back of the console. Is it the same fix? Where is the hearer getting the ice-cold air to blow out just that one vent?

Nik

the dash board must come out.

My '87 does not blow anything out of the back vent. Is this a vacuum actuator problem? If so, how do you get to it? Sleepwalker, were you saying that the dash has to come out to get to this? It's not a big deal to me, so I'll probably let it go if it's a pain to get to.

In a related story, I found my problem with the A/C not working and the aux fan running continuously. Thanks to the forum, I tried unplugging the temp sensor on top of the thermostat housing. One plug made the a/c start running, and the other stopped the aux fan from running. :) I'm very happy that it's only a $35 that I can replace. This forum rocks!!!

Thanks to everyone who posts on here. The suggestions are extremely helpful.

the back vent should only be for the warm air?

Oh, I see. I looked in the manual and I could not find anything about it. I figured it would be in a diagram somewhere, as everything else is well documented. Thanks for the tip.

here's what it looks like with the dash out. you can actually get to most of them with most of the dash installed, just harder.
http://users.adelphia.net/~karasz/dashout126.jpg

with the whole thing out, it is now easy for you to find the flap that causes the problem.



local://upfiles/1/A4AB7F05605445C8AFEEDCE34638B6C5.jpg

Mine had that exact problem. To fix it right......you will need to isolate which vacuum under the dash is malfunctioning. More than likely, it is the vacuum that is right under the driver's side steering wheel. You will have to remove the carpeted cover to see it (only a few screws). The vacuums are not cheap. I fixed it (kinda) the FREE way. I disconnected the vacuum in that location and now it blows out of all vents at the same time. I can still shut off vents with the cut-off levers but I cannot use the control unit to switch back and fourth. It works for me.....I was just happy to finally have good cold air blowing in my face! Another problem that could cause this issue would be a control unit malfunction. Good luck and stay cool

From looking at the pic, buymbparts.com is right. A easy DIY project!