Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Mercedes-Benz SL Discussion Forum

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 06-17-2007, 05:36 PM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
1991 300SL air vents defaulted to defrost

The climate control decided to direct all of the air to the defrost vents no matter if in automatic or not and not matter which manual button I push.

Has any one experienced this problem and what was the fix?

Thanks all,

sldan
Reply With Quote
  #2  
Old 06-18-2007, 08:17 PM
waybomb's Avatar
Registered User
 
Join Date: Nov 2002
Location: St. Joe, MI; Manitowoc, WI
Posts: 1,553
On my 126, it was a major vacuum leak. It's sort of a safety feature - if vacuum is lost, at least the windows will be defrosted.
__________________
Thank You!
Fred
2001 E430 Sport, 204,000 miles
1997 C280 Sport, 144,000 miles
1991 300SL, 189,000 miles
1987 420SEL, 149,000 miles
1986 190e 2.3 16v, 151,000
1968 W30 442, 78,000 miles
1988 46' US1 Cougar, 3 supercharged 572's
http://s4.photobucket.com/albums/y145/waybomb/
Warming the globe, 24 cylinders at a time
And I want a 126 wagon! Point me to one!
Reply With Quote
  #3  
Old 06-18-2007, 09:47 PM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
Thanks Fred,

I plan to look into this over the weekend.

sldan
Reply With Quote
  #4  
Old 06-19-2007, 10:57 AM
Registered User
 
Join Date: May 2001
Location: Las Vegas, Atlanta
Posts: 669
Hey Dan. Take a look at this post: Climate control diagnostics on '90 - '95 R129 SLs. It shows how to run diagnostics on your climate control system.
Reply With Quote
  #5  
Old 06-19-2007, 05:37 PM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
Thanks Bob.

I purchased a Service CD but have had trouble using it since I have a too new version of Abobe and I have not bothered to sort that issue out yet.
Reply With Quote
  #6  
Old 06-27-2007, 08:09 AM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
I do have a vacuum leak.

Any ideas on how to isolate the problem and can I replace a single actuator?

sldan
Reply With Quote
  #7  
Old 06-29-2007, 02:09 PM
Registered User
 
Join Date: May 2001
Location: Las Vegas, Atlanta
Posts: 669
You can isolate the problem with a tool that is a combination vacuum pump/gauge, Dan. One can be purchased at an auto parts store or borrowed from Autozone at no charge. To check for a leak you use the pump to apply vacuum and watch to see if the vacuum holds.

You can purchase and replace the flap actuators individually.
Reply With Quote
  #8  
Old 06-29-2007, 03:04 PM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
Thanks Bob,

I finally can use my service CD and found all of the info in the climate control system.

I will muster up the courage to take the dash board off and get to it.

Ok on the hand pump. I will pick one up.

Thanks,

sldan
Reply With Quote
  #9  
Old 07-15-2007, 07:56 PM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
Update on troubleshooting.

It appears that the 15 port switchover unit is not working.

Does anyone know of there is a way to tell if the switchover unit is defective or the climate control unit is not sending information to the switchover unit?

Has anyone had to replace a 15 port switchover unit or climate control unit?

If so what was the cost.

I have come to the conclusion that I do not have a vacuum leak but rather the switchover unit is not switching after checking for troubles codes and there were none. My vent controls are OK and I have good vacuum on the green/yellow tube to the switchover unit.

The CCU controls the fan OK and all other functions seem to work except that the vents do not respond to the position controls and all air goes out the defrost and side vents.

Tanks,

sldan
Reply With Quote
  #10  
Old 08-18-2007, 08:14 AM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
How do I remove the carpeted curved piece that is directly under the airbag?

I have removed the two 8mm bolts and the bottom of the carpeted piece is loose but it appears to still be attached at the top or sides.

Thanks in advance,

Dan
Reply With Quote
  #11  
Old 09-10-2007, 08:40 PM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
Finally found and fixed the problem.

The vacuum switchover valve located under the airbag was defective.

PN 129-800-06-78.

This device distributes the vacuum to the various vacuum elements which controls all of the vent, defroster, blending, and floor flaps.

I did not have any trouble codes in the main control unit and did not have a vacuum leak.

Thanks to all.

Dan
Reply With Quote
  #12  
Old 09-10-2007, 09:04 PM
Registered User
 
Join Date: Mar 2003
Location: Milwaukee Wisconsin
Posts: 1,150
Good detective work. Behind passenger side air bag? How did you finally decide it was this particular part? A bit of analysis please.
__________________
Resistance is Futile.
Reply With Quote
  #13  
Old 09-11-2007, 07:14 AM
Registered User
 
Join Date: Oct 2002
Location: Columbus, Ohio
Posts: 155
It is located under the passenger side airbag and the cost for a new unit was$377 with dealer discount. I could not find a re-manufactured one. Apparently this part does not fail often.

Using the service CD, I used a process of elimination and luck.

First I did the trouble code, potentiometer, and sensor checks on the control unit and all was OK. There were no codes and all of the signals were within range.

I bought a hand operated vacuum pump and checked for vacuum leaks on all of the vacuum lines from the switchover valve to each actuator. This was the hardest part because I had to take out the airbag, stand on my head to remove the passenger side carpeted piece under the air bag which required removing the radio, the climate control control unit, and the center vent to get to all of the screws. I had no vacuum leaks.

I also checked the vacuum pump in the trunk and the vacuum distribution block. Both were OK.

The remaining component in the system is the vacuum switchover valve. It operates on voltage pulses sent by the climate control unit. Since there were no trouble codes from the Climate control unit and no vacuum leaks, I rolled the dice and ordered the switchover valve.

Then I had to stand on my head again to put things back together.

It took less than 1 minute to replace thje switch over valve and an hour to put thing back together.

sldan
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 01:35 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page