PeachParts Mercedes-Benz Forum - View Single Post

bhatt · #5 03-14-2006, 03:14 PM

I just did a quick search and found the info that helped me fix mine.. sounds VERY similar to the problem you're having and the steps you've already followed.

By the way, I believe Dr. Booth is a member of this forum also. He tends to know his stuff REALLY well!

QUESTION:
Date: Tue, 24 Jul 2001 08:44:53 -0500
From: "John Winn"
Subject: [DIESEL] 1987 300SDL trans kickdown problem..

Hello group,
I have had this intermittent problem since I bought this car and yesterday
replaced the kickdown switch on the floor, thought it fixed it but this
morning back to not working..The transmission kickdown would only work
intermittently. When it would decide to work it worked great..I figured the
first thing I would try was a new switch. Went from not working to working
just by popping in the switch, figured that was it..Is the only component
other than the switch the solenoid or is there some "computer box" that
controls this? I think I read somewhere that it is supposed to control the
AC compressor too. Is the solenoid on the trans something I can change
myself? I hope someone might have an idea, the car really doesn't have a
lot of low end "git up and go" without this working...Thanks in advance!!!!
John
I can't believe the transmission is not even mentioned in the repair manual
CDs...

ANSWER:
Date: Tue, 24 Jul 2001 10:40:06 -0400
From: Marshall Booth
Subject: Re: [DIESEL] 1987 300SDL trans kickdown problem..

John, HAVE you changed ALL the fuses?!!! There is NOTHING
you can do more cheaply and you have a better then 50:50
chance of correcting the problem. Fuse 7 on a W124 is the
fuse that controls it (I'll have to check on the CD for a
W126 - it's fuse 5) and there is interaction between the
KLIMA relay and the kickdown switch! The kick down switch is
powered from pin 6 on the KLIMA relay and is diagramed in
the W124 climate control compressor clutch control drawing
in the Electrical Troubleshooting Manual (I don't have a
W126 electrical manual but it can be located on Fig. 83/25a
in the W126 climate control manual on page A6). There is a
note that refers to the KLIMA/kickdown circuitry ONLY
existing in the '86 model year (these notes have not been
entirely reliable in the past, but I wouldn't entirely
discount them either). Back to the W126 CD to see if there
is a reference to the kickdown switch in the MAIN electrical
index. File ETM/126from86.pdf shows this KLIMA to kickdown
switch/solinoid circuitry for W126.125/134/135 from MY '86
through '91 but it is NOT clear what particular signal to
the KLIMA relay interrups the kickdown signal. Based on the
experience I've had with multiple W201s and a W124 (with
much of the same wiring and relay layout and essentially the
same circuitry with MINOR modifications) I would pull the
KLIMA and overvoltage protection relays and clean the pin
contacts and be sure that the female "sockets" have not lost
position within the socket attached to the chassis and that
they are FIRMLY grasping the male pins that plug into them
(if replacing fuses doesn't cure the problem). I have had
this problem intermittantly on my '87 190D 2.5 NON-turbo but
I solved it - I swapped the automatic transmission for a 5
speed manual and now don't have ANY use for a kickdown
switch ;-)

Marshall
- --
August M. Booth, Jr. Ph.D.