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 > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 07-25-2010, 05:05 PM
Jeremy5848's Avatar
Registered Biodiesel User
 
Join Date: Mar 2006
Location: Sonoma Wine Country
Posts: 8,402
W124 Climate Control Vacuum Valve Repair DIY

On a recent trip to the "Pick and Pull" DIY auto scrapyard at Windsor here in northern California I discovered a new climate control failure mode (as if there weren't enough already). I had decided to pick up an extra vacuum control valve for my 1987 300D Turbo (W124, OM603). This thing, which Mercedes calls "Y7 Switch-over Valve Unit," controls the vacuum to all of the pods that open and close the various 'doors.' Where the 123 has individual valves, the 124 has a set of seven valves built into a vacuum manifold and mounted on the right (passenger) side of the air box. You can see it if you remove the glove box liner. If you have an air bag there (late 124) you must remove the right side under-dash panel.





When I got home from Pick and Pull, I tested the thing and discovered that two of the valves didn't work. I went back and exchanged it for another, only to discover a similar problem. I ended up buying a third before I found one that was completely good but decided to keep the second (they were only $6.49 each) so I could experiment. I was surprised that these things went bad -- they're so simple -- and worried that mine might be bad, too, even though my climate control seems to work correctly.

The manual tells us that these things are non-repairable and indeed the plastic case is heat-sealed together -- no cover to unscrew, very un-Mercedes-like. It was clear to me (from an examination of the 8-pin plug) that a pc board ran the length of the manifold, connecting the plug to all of the vacuum solenoids with one pin common. I immediately thought "cold solder joint" but how to get inside? I finally decided to do the job semi-destructively and cut off the back with my bandsaw.





This could also be done with a hand saw or a sabresaw but you'd have to have very steady hands. With the back off, I could see that there really was a pc board "spine" and I could test all of the connections.





Each solenoid tested good (12 Volts across its pins and it went 'click') but as I carefully examined the connections, I saw one very obvious cold solder joint. Here is what it looks like in a low-power zoom microscope (hold digital camera up to eyepiece).





With the problem identified, it will be easy to refresh all of the solder joints. I'll then smear silicone sealer all over the plastic back and glue it back over the manifold.

If your climate control system is not working correctly, you now know that it could be one or more of three things: a bad push-button unit, one or more bad vacuum pods, or a bad manifold. You can test the valves without removing the manifold and all the vacuum lines. This requires removing the right under-dash panel so you can get at the plug that goes into the manifold.

With the plug removed, you will see eight pins in two rows of four. One of the pins is common positive (see middle image in three-view photo above), each one of the others is the ground for one solenoid. To test the valves, connect the common pin to a 12 Volt battery (either the one in the car or a portable battery) and then touch each of the other seven pins one at a time to the other terminal of the battery. For testing it doesn't matter whether common is positive or negative. Listen closely -- each solenoid should "click" and you might get a little spark at the pin. Any pins that don't produce a "click" indicate a bad solenoid.

Again looking at the center image above, the pins are connected to the numbered solenoids in this order:

2 -- 4 -- 6 -- Common

1 -- 3 -- 5 -- 7

The solenoids do the following functions. This may help you diagnose your particular problem.

1 Fresh air/Recirculated (short stroke)
2 Fresh air/Recirculated (long stroke)
3 Diverter (no, I don't know what it does either)
4 Center dash outlets
5 Legroom outlets
6 Defroster outlet (long stroke)
7 Defroster outlet (short stroke)

A few notes: The manifold is only clipped to the side of the airbox. It pulls off fairly easily. Keep track of which vacuum line is connected to which valve (even though the label and the lines are color-coded). Be careful unplugging the electrical connector.

The alternative is to buy a new solenoid valve assembly from AllPartsExpress for $168.30. My advice: Learn to solder!

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
Reply With Quote
  #2  
Old 07-25-2010, 06:32 PM
Registered Hack
 
Join Date: Mar 2008
Posts: 4,642
I am struggling with the same exact problem in my W201. Thank you for being an electrical genius.

My 1984 has an outdated, cantankerous Y valve similar to the one shown. The later models have been updated and the arrangement has changed but all the pins remain the same.

Can I post pictures so we can review this? It is very similar, and perhaps you might suggest that I simply re-trace my unit.
Reply With Quote
  #3  
Old 07-25-2010, 07:26 PM
compress ignite's Avatar
Drone aspiring to Serfdom
 
Join Date: Feb 2004
Location: 32(degrees) North by 81(degrees) West
Posts: 5,554
Thank You ,Fearless one.

For delving,where no one else treads!
__________________
'84 300SD sold
124.128
Reply With Quote
  #4  
Old 07-25-2010, 07:57 PM
Aquaticedge's Avatar
Bump on a log
 
Join Date: Nov 2009
Location: See Biography
Posts: 3,148
I got a few of these buggers since mine had failed, cool to see what one looks like though
__________________
hum.....
1987 300TD 311,000M Stolen. Presumed destroyed
Reply With Quote
  #5  
Old 07-25-2010, 08:55 PM
Jeremy5848's Avatar
Registered Biodiesel User
 
Join Date: Mar 2006
Location: Sonoma Wine Country
Posts: 8,402
Photos

Quote:
Originally Posted by jt20 View Post
I am struggling with the same exact problem in my W201. Thank you for being an electrical genius.

My 1984 has an outdated, cantankerous Y valve similar to the one shown. The later models have been updated and the arrangement has changed but all the pins remain the same.

Can I post pictures so we can review this? It is very similar, and perhaps you might suggest that I simply re-trace my unit.
Yes, please reply to this post and add your own pictures. Many of the parts on the W124 were first used in the W201 -- there are many similarities and also many differences. You can use the forum itself to host up to five pictures per post but the pictures are limited to 800x600 pixels and no more than 72 KB each. You can also use a service like Photobucket and have the pictures larger. I do both. The pictures in this thread are hosted by Photobucket.

I pulled the glovebox and lower dash panel and did the acid test on the solenoid valve in my '87. Fortunately, all seven valves made a satisfying "click." Here's a picture of what the solenoid valve looks like installed in the car and with the plug unplugged. I had to scrunch down in the footwell to get the picture. Of the eight pins you can see, the one in the upper right corner is common and the other seven each go to one of the solenoids. Putting 12 Volts between the common pin and one of the others should get you a nice "click." Any one that doesn't "click" means a bad solenoid (unlikely) or a bad solder connection.

Jeremy


__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
Reply With Quote
  #6  
Old 07-25-2010, 10:20 PM
Registered User
 
Join Date: Jan 2010
Location: Moncure, NC (near Raleigh)
Posts: 350
Nice work Jeremy!!!
__________________

1987 300TD 147,000 miles- Palomino leather interior, 1995 facelift and body cladding, E350 wheels, Rebuilt suspension and sport springs, rebuilt turbo, New Monarch injection pump and injectors....and the list goes on and on...
Reply With Quote
  #7  
Old 07-26-2010, 01:18 AM
Registered User
 
Join Date: Jul 2010
Location: Vicenza, Italy
Posts: 22
Nice work, Jeremy. I'm sure I'll have to do the same to my W124 as my fresh air/recirculation switch appears to have no effect on the air. It's either this or a vacuum module- not sure what else it could be.

Another gremlin I have is I cannot get the highest airflow to work in manual mode. It 'works' in auto mode but it takes a few minutes before the air flow will get to the highest output. Not quite sure if it's related (ie- due to various doors not fully opening/closing, or due to an a/c logic system not kicking in) but I'll play with it soon.
__________________
1993 E250 2.5L TD 230,000 kilometers
Vicenza, Italy
Reply With Quote
  #8  
Old 07-26-2010, 01:25 AM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,841
I have the reverse problem. I set the ACC to max heat or cold and the blower blows hard. I press the max blower button and it kicks into a still higher speed.

Sixto
87 300D
Reply With Quote
  #9  
Old 07-26-2010, 04:31 PM
Jeremy5848's Avatar
Registered Biodiesel User
 
Join Date: Mar 2006
Location: Sonoma Wine Country
Posts: 8,402
As he describes it, Sixto's system is working correctly. "Low" gives you the slowest blower setting, "High" gives maximum, and "Auto" handles everything in between. It's interesting that the input to the "porcupine" blower controller is 12 Volts and ground plus a third wire from the PBU which varies from about 1 Volt to 3 or 4 Volts (I took notes on this once but cannot find them at the moment). The Porcupine (which must be a honkin' big transistor) uses the voltage input from the PBU to limit the current delivered to the blower from our friend, fuse 12 (or the external 30A strip fuse).

Incidentally, it's fairly easy to put a potentiometer in this third wire to change the control voltage manually. Push the "High" speed button and dial the blower to wherever you want it like changing the volume on the radio. Only challenge is finding a control that will go in the dash and look like it's stock Mercedes, or hiding the control so no one can see it.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
Reply With Quote
  #10  
Old 07-27-2010, 08:21 PM
Registered User
 
Join Date: Jul 2009
Location: Dutchess County, NY
Posts: 38
Thank you for this thread and your work, Jeremy. I have intermittent center vents on my '87 and was certain I needed to pull the dash to replace a bad vacuum pod--a job I dread for some reason. At the very least you have given me some hope that the repair may be more easily accessible.

Thanks again.
__________________
-RK
'83 240D, auto, 170,000 miles "Old Blue"
'87 300TD, 140,000 miles
Reply With Quote
  #11  
Old 07-27-2010, 10:58 PM
Jeremy5848's Avatar
Registered Biodiesel User
 
Join Date: Mar 2006
Location: Sonoma Wine Country
Posts: 8,402
Options

Quote:
Originally Posted by fullcircle View Post
Thank you for this thread and your work, Jeremy. I have intermittent center vents on my '87 and was certain I needed to pull the dash to replace a bad vacuum pod--a job I dread for some reason. At the very least you have given me some hope that the repair may be more easily accessible.

Thanks again.
If it turns out to be the vacuum pod (and while you have the glove box out), consider reaching up into the rubber boot that connects the center vents to the climate control box and jamming that door open. I did that on my '87 and it worked that way for over a year. Because the vacuum pod was bad (leaking) I also removed that vacuum line at the solenoid block and put a cap over the outlet (I think it's #4).

When I later replaced the dash, I also replaced most of the pods but tee'd the center one into the solenoid input line so it sees vacuum all the time. Thus I have center vent heat and if I ever want to put the system back to stock, all I have to do is reroute a couple of vacuum lines, working through the glove box opening.

Dash replacement is much easier the second time. If you have access to a DIY junkyard, go practice there. Print out and take along one of the good DIY threads from this forum (Sixto's is one of the best) and have at it. When you later do your own you'll be much more confident and less likely to make a serious mistake.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
Reply With Quote
  #12  
Old 07-28-2010, 05:03 PM
Registered User
 
Join Date: Jul 2009
Location: Dutchess County, NY
Posts: 38
Those are excellent ideas and good advice. Unforunately, I'm in a part of NY that doesn't have any pick-n-pull yards (at least that I've found yet). I'm envious of the folks who have them. I've read sixto's dash removal procedure and plan on using it if needed, but I think that is why I dread the job....no more blissful ignorance--- I'm hoping it's electrical, but will take your advice of jamming the flap open to put off the job for awhile if it is vacuum related. Thanks again for the help.
__________________
-RK
'83 240D, auto, 170,000 miles "Old Blue"
'87 300TD, 140,000 miles
Reply With Quote
  #13  
Old 07-29-2010, 03:00 PM
Registered Hack
 
Join Date: Mar 2008
Posts: 4,642
W201 Valves

The first three pictures are of my currently installed valve, the fourth is my backup / replacement.

I am not sure how to test still based on what you have offered. Maybe I didn't read very well. All the solder joints on the old valve are accessible without cutting any panels off.

How can I test the newer one without cutting a panel off?




Attached Thumbnails
W124 Climate Control Vacuum Valve Repair DIY-y-valve-201-001.jpg   W124 Climate Control Vacuum Valve Repair DIY-y-valve-201-002.jpg   W124 Climate Control Vacuum Valve Repair DIY-y-valve-201-003.jpg   W124 Climate Control Vacuum Valve Repair DIY-y-valve-201-004.jpg  
Reply With Quote
  #14  
Old 07-29-2010, 03:32 PM
Registered Hack
 
Join Date: Mar 2008
Posts: 4,642
Opened

These valves were very 'Mercedes-like'.

few screws and opened right up.

I think I can see the 'common' that Jeremy identified in his valve. I think I know how to test it now.


Thanks, Jeremy!




Attached Thumbnails
W124 Climate Control Vacuum Valve Repair DIY-y-valve-201-005.jpg   W124 Climate Control Vacuum Valve Repair DIY-y-valve-201-006.jpg   W124 Climate Control Vacuum Valve Repair DIY-y-valve-201-007.jpg  
Reply With Quote
  #15  
Old 07-29-2010, 04:23 PM
Jeremy5848's Avatar
Registered Biodiesel User
 
Join Date: Mar 2006
Location: Sonoma Wine Country
Posts: 8,402
Interesting! Looks like the 201 has a different kind of valve. Still made by Eaton but easier to repair, I'm jealous. What model and year of 201 do you have?

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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 01:07 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