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 08-07-2009, 01:08 PM
bustedbenz's Avatar
Registered User
 
Join Date: Feb 2007
Location: Lexington, NC or Boone, NC
Posts: 2,272
Gas W126 climate control in diesel?

In chasing my climate control problems (A/C is cold when it works, but cuts out fairly early in a trip and can never be persuaded to re-engage) I've decided to try a different dashboard "computer" -- replace the control box and see if it's sending bad signals to the system. Doesn't cost me anything to try, IF I can use the parts I've got.

I went to pull-a-part two or three weeks ago and got a climate control unit that looks like it's in MUCH better shape than mine. The buttons press more firmly, it wasn't covered in dust, the temperature wheel has a firmer rotation and clicks into the detents more strongly; it appears to just be generally less worn out and possibly okay. There's a tag on it that says it was inspected and found okay in 2001, which means it was somebody's rebuild/replacement. Point is, I'm optimistic enough to assume it works at least as well as mine does until I learn otherwise.

Here's the catch. It's out of a gasser w126, not sure which one or what year but I think it was late 80s. I know for a fact that it's the same "generation" of w126 as mine, rather than the older one. I haven't checked each plug to see if they match but IIRC from last time I had mine out a year ago, they seem to. It has the exact same complement of rocker switches up at the top for defrost, hazards, etc; in the same order with the same markings, so I'm assuming they're identical switches if the pins all line up. (I just took the thing out with the whole wood trim piece and all the switches, since the wood looks better than mine too. Going to change it in as a unit.)

Is there any reason that shouldn't work? The only visual difference I see between my button box and the potential gasser replacement is that mine has a very thin "O" marking on the off button, whereas this one seems to have been printed in "bold". Everything else seems identical as near as I can make out. Does somebody know that they in fact do completely different things under the dash or run on a different voltage or something? If I were an engineer, I'd put the same climate mechanisms in any w126 no matter how it was powered, but I can't assume that without somebody saying "Sure, try it, you won't shred anything."

__________________


http://www.appstate.edu/~salleyms

"What could possibly go wrong?"

~Michael S.~ -
1986 M-B 300SDL, retired due to rust and electrical problems. Donated engine to:
1987 M-B 300SDL, odo dead. New project.
1982 M-B 240D, odo stopped at 308,000
1982 M-B 300SD, 175,000
1989 Dodge Ramcharger, 87,000 - 4wd, 318
Reply With Quote
  #2  
Old 08-07-2009, 01:16 PM
compu_85's Avatar
Waiting for his Model 3..
 
Join Date: May 2008
Location: Springfield VA
Posts: 5,174
It should work just fine, all the Gen 2 W126s have the W124 climate control system, gas or diesel.

-J
__________________
1991 350SDL. 230,000 miles (new motor @ 150,000).

2013 Fiat 500E. 20,000 miles, 80 miles at a time.
2012 Passat TDI. 95,000 miles. More space, power, and fuel economy than the Benz
2004 Touareg V10 TDI. 150,000 miles. One of 450.
1999 Jetta TDI. 310,000 miles.
1992 Jetta ECOdiesel. 156,000 miles. 1 of 48. Sold.
1991 Jetta ECOdiesel. 430,000 miles. 1 of 700. Sold to VeeDubTDI, totaled in front of our house
Reply With Quote
  #3  
Old 08-07-2009, 01:18 PM
tbomachines's Avatar
ಠ_ಠ
 
Join Date: Mar 2009
Location: Philadelphia
Posts: 6,660
It should plug right in. What other troubleshooting have you done so far? Have you tackled the KLIMA?
__________________
TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth
Reply With Quote
  #4  
Old 08-07-2009, 01:29 PM
bustedbenz's Avatar
Registered User
 
Join Date: Feb 2007
Location: Lexington, NC or Boone, NC
Posts: 2,272
Quote:
Originally Posted by tbomachines View Post
It should plug right in. What other troubleshooting have you done so far? Have you tackled the KLIMA?
No, I haven't. I can't even physically locate the KLIMA at the moment. I haven't really had time to troubleshoot it, and what time I have spent on it has been in trying to further my guesses about whether I'm looking at head gasket or head problems. (Still waiting on an oil report.)

I've just checked every fuse I can find to prove that they're good, and I've put gauges to it and verified that my freon levels are adequate to be cooling at least somewhat.

The trouble I've got is that the compressor works but doesn't seem to stay engaged; it just randomly (no button pushing from me) clutches out and never comes back the rest of the day. Engine restarts don't help, pushing every button on the box doesn't help... it just dies. So I figure it's got to be electrical somewhere. Figured the computer was as good a place to start as any, since it is already showing signs of not working right. Specifically -- it works fine all summer, but any time the ambient temperature is below 40F or so and I start the car, it takes 20 minutes before the system responds to me at all. It doesn't matter which button I push; if it's cold outside (when I desperately need heat on the glass to make it safe to drive) it simply doesn't do anything. And when it does engage on those days, it does so with a HUGE flurry of relays clicking in and out rapidly, the blower motor starting, stopping, starting, stopping, starting, etc... and just generally a whole demonstration of electrical foolishness. And then when it does finally settle down frequently it's stuck in "heat" mode for 15 minutes until I either pass out from the temperature or it finally realizes i asked it to cool down half an hour ago.

So all this suggests that my button box needs replacing even if I still have other problems. If the compressor cut-out doesn't stop doing that when I put the new computer in, I'll keep troubleshooting.
__________________


http://www.appstate.edu/~salleyms

"What could possibly go wrong?"

~Michael S.~ -
1986 M-B 300SDL, retired due to rust and electrical problems. Donated engine to:
1987 M-B 300SDL, odo dead. New project.
1982 M-B 240D, odo stopped at 308,000
1982 M-B 300SD, 175,000
1989 Dodge Ramcharger, 87,000 - 4wd, 318
Reply With Quote
  #5  
Old 08-07-2009, 01:54 PM
Banned
 
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
It plugs right in alright...........but, I believe the logic is different on the gasser. The diesel provides a ground signal to the Klima to allow it to close. The gasser provides +12V for the same task.

I do not believe that they can be exchanged. Check the part number............probably different than the diesel.
Reply With Quote
  #6  
Old 08-07-2009, 01:57 PM
pawoSD's Avatar
Dieselsüchtiger
 
Join Date: Oct 2004
Location: Grand Rapids, MI
Posts: 15,315
Quote:
Originally Posted by Brian Carlton View Post
It plugs right in alright...........but, I believe the logic is different on the gasser. The diesel provides a ground signal to the Klima to allow it to close. The gasser provides +12V for the same task.

I do not believe that they can be exchanged. Check the part number............probably different than the diesel.
Why would they make that backwards between the two?

You could always use a relay to reverse that instruction.
__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 90k - mine - (OC-91,200)
'17 Metris(VITO!) - 18k - wifes (OC-25k)
'01 E320 Wagon - 161k - mine (OC-165,000)
'01 E320 - 180k - dad's (OC-182,500)
'07 E350 Wagon - 134k - dad's (OC-139,500)
'01 SL500 - 56k - dad's (OC-59,000)
'16 E400 4matic Sedan - 81k - Brothers (OC-88,000)
Reply With Quote
  #7  
Old 08-07-2009, 08:47 PM
Custom User Title
 
Join Date: Jun 2008
Location: Simi Valley, CA (SoCal)
Posts: 454
It might not hurt anything, but the part numbers between a 88 420 SEL and 86 SDL are different. Check the wiring schematics in the FSM, the troubleshooting section should have good schematics. Or take the covers off and look inside. If they are different, it shouldn't take too much inspection to make that determination.

I'd verify that the tests in the FSM pass or fail before adding an unknown (the gasser ACC) into the mix. You should be able to test the climate control system with a multimeter if you know what you're doing. Might have issues with the monovalve - when mine was sticking open it would give me heat with the temp wheel turned all the way cold, and the hotter the interior got, the faster the fan would blow making it even hotter. Well, the control unit didn't know that the monovalve wasn't working, it just knew that it was hot, and that it needed more air to cool it off. My point is that you need to check all your inputs to the control unit before you decide it's bad. And by the same token, you need to check that when the control unit sends a signal to a relay that the relay actuates and performs its intended function.

I haven't looked at the schematics in this particular case, but usually 12V is hard wired to a relay and a ground is used to actuate it. So now I've just given a SWAG instead of fact which I think puts me in the category of Senior Member. Woo-hoooo!
__________________
mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)
Reply With Quote
  #8  
Old 08-07-2009, 09:00 PM
daw_two's Avatar
diesel enthusiast
 
Join Date: Jan 2007
Location: Germantown, TN
Posts: 5,444
echoing Brian

I'm going to echo Brian because I think I tried that last year.......Gassers are a different part number and I am SURE I looked this up in EPCnet.
__________________
daw_two
Germantown, TN

Links:
Current Car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more
Reply With Quote
  #9  
Old 08-07-2009, 10:12 PM
Registered User
 
Join Date: Sep 2004
Posts: 8,731
Quote:
Originally Posted by bustedbenz View Post
In chasing my climate control problems (A/C is cold when it works, but cuts out fairly early in a trip and can never be persuaded to re-engage)
I had that problem. Turned out to be a bad evaporator temp regulator.

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 11:25 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, 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