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 > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 03-15-2005, 05:50 AM
Registered User
 
Join Date: Sep 2004
Posts: 162
A/C Vents closing and getting only defrost when I accelerate?

I have a 98 CLK 320 and when I go full throtle, the vents all close up and the defrost kicks in. Any idea on how to diagnose this problem? Or even better....the fix? Thanks guys...

Reply With Quote
  #2  
Old 03-15-2005, 07:42 AM
Geezer
 
Join Date: Aug 2000
Location: Holland, MI
Posts: 1,316
I don't know a thing about newer cars, but I'll guess.

Sounds like the vacuum dashpots are sensing low vacuum from your manifold and reverting to the 'fail safe' mode of Defrost when vacuum is low.

That said, I'll guess there is a vacuum accumulator that is intended to sustain vacuum for the HVAC system during full-throttle low-manifold vacuum conditions, and the accumulator or a dashpot has a leak, giving you the results you report.

In short, a vacuum leak in the HVAC tubing is where I would be looking.

I will delete this post when someone who knows this car better can set you straight, since I'm only guessing.

Best Regards,
Jim
Reply With Quote
  #3  
Old 03-15-2005, 08:46 AM
I told you so!
 
Join Date: Jun 2002
Location: Motor City, MI
Posts: 2,853
Like Jim's post, this is a guess also, but I believe some designs use a check valve in the vacuum line that is supposed to maintain the vacuum to the HVAC system when vacuum disappears momentarily. If you find such a check valve, you should be able to suck air through it in one direction but not the other.
__________________
95 E320 Cabriolet, 159K
Reply With Quote
  #4  
Old 03-16-2005, 12:47 AM
Registered User
 
Join Date: Feb 2003
Location: Michigan
Posts: 44
I have the same issue in my 1997 E320. I agree that vacuum is probably the cluprit, just do not know where to start. Has anyone had this problem and solved it?
Reply With Quote
  #5  
Old 03-16-2005, 08:10 AM
Moderator
 
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Cool

Vacuum loss is the problem & a VERY common one!

On the CLK try depressing the EC button & see if the center vents still close durning accel, IF not then the fresh air vacuum element is the problem!

The starting point is to find the vacuum block under the passenger under-dash panel & by using a vacuum pump check each vacuum line & vacuum element for leaks.
__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator
Reply With Quote
  #6  
Old 03-16-2005, 10:21 PM
Registered User
 
Join Date: Feb 2003
Location: Michigan
Posts: 44
I reference the WIS program and located the swithover valve block, the W210 with automatic air has 14 connections. Can you expound a little on the testing procedure using a vacuum pump. Any recommendations on a pump? I assume a rather inexpensive hand pump would suffice.
Reply With Quote
  #7  
Old 03-17-2005, 08:44 AM
Registered User
 
Join Date: Sep 2004
Posts: 162
Vacuum elements...

Does the dash need to be removed to access the vacuum elements?
Reply With Quote
  #8  
Old 03-17-2005, 10:35 AM
Registered User
 
Join Date: Feb 2003
Location: Michigan
Posts: 44
According to WIS, it is located under the glove box. You probably just need to remove that cover above the footwell and maybe the knee bolster.

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 01:01 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page