Author Topic: Automatic Transmission Electric Stuff  (Read 6551 times)

JimVillers

  • Full Member
  • Gold
  • *****
  • USA, VA, Virginia Beach
  • Posts: 573
Automatic Transmission Electric Stuff
« on: January 14, 2010, 22:36:02 »
Checking the wires, switches and solenoids, I could not find a wiring diagram for the automatic transmission and I wanted to sort out how it worked.

It appears that the two pressure switches are wired in parallel and the wire disappeared into the harness.

It appears that when the throttle body idle switch is closed that the double acting solenoid on top of the transmission will push the rod down.  When the accelerator pedal switch is closed (full throttle) that the double acting solenoid will pull the rod up.       

I wondered what was the purpose of the two pressure switches and how they are wired into the circuit?
Jim Villers
190SL, 230SL 5-Speed, MGB 5-Speed, MGB GT V8 RHD (real MG), 2016 SLK

ja17

  • Full Member
  • Platinum
  • ******
  • USA, OH, Blacklick
  • Posts: 7384
Re: Automatic Transmission Electric Stuff
« Reply #1 on: January 15, 2010, 00:52:42 »
Hello Jim,

One pressure switch is for reverse, the other is for forward.  They complete the ground (earth) to the idle speed solenoid on the intake linkage and increase the idle speed when the car is in forward or reverse.
They are the source of the negative ground (earth) since they are bolted to the transmission. Yes they are wired in parallel.

The function changed on the later USA cars, a dash pot was added to the intake to increase idle speed in gear. The linkage solenoid was then used to increase idle speed when the AC was turned on.

As far as the wiring on the pressure switches, they are tied in parallel with one wire between the two and then onto the terminal block of the transmission with another "grun" & "rot" wire that goes to the intake  linkage solenoid. It should be one of the wires with a 4.3mm inside diameter ring terminal hole . There are three different ring terminal hole sizes.

  Power to the linkage solenoid comes from the fuse box #5 via a "swartz"/"grun"/ "rot" wire.

« Last Edit: January 15, 2010, 02:25:36 by ja17 »
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

JimVillers

  • Full Member
  • Gold
  • *****
  • USA, VA, Virginia Beach
  • Posts: 573
Re: Automatic Transmission Electric Stuff
« Reply #2 on: January 15, 2010, 02:24:43 »
Joe .... Thanks, now I understand why two pressure switches and what they are for.  Everything is simple when you understand.
Jim Villers
190SL, 230SL 5-Speed, MGB 5-Speed, MGB GT V8 RHD (real MG), 2016 SLK

Cees Klumper

  • Full Member
  • Platinum
  • ******
  • USA, CA, De Luz and Los Angeles
  • Posts: 5679
    • http://SL113.org
Re: Automatic Transmission Electric Stuff
« Reply #3 on: January 15, 2010, 06:24:19 »
Everything is simple when you understand.

Reminds me of that famous (well, in The Netherlands) quote from our all-time great soccer player, Johan Cruyff: "you only get it once you understand it".

Joe to me illustrates once again how much there really is to know about our cars. What I don't get is how he remembers it all!
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II

jeffc280sl

  • Guest
Re: Automatic Transmission Electric Stuff
« Reply #4 on: January 16, 2010, 03:56:27 »
I hope this pic helps.

JimVillers

  • Full Member
  • Gold
  • *****
  • USA, VA, Virginia Beach
  • Posts: 573
Re: Automatic Transmission Electric Stuff
« Reply #5 on: January 16, 2010, 14:20:50 »
Jeff ..... Thanks for getting me to look in the correct area of the manual.  I found the exact diagram that I was looking for.
Jim Villers
190SL, 230SL 5-Speed, MGB 5-Speed, MGB GT V8 RHD (real MG), 2016 SLK

mdsalemi

  • Pagoda SL Board
  • Platinum
  • ******
  • USA, NC, Davidson
  • Posts: 6944
Re: Automatic Transmission Electric Stuff
« Reply #6 on: January 16, 2010, 14:27:51 »
Reminds me of that famous (well, in The Netherlands) quote from our all-time great soccer player, Johan Cruyff: "you only get it once you understand it".

Joe to me illustrates once again how much there really is to know about our cars. What I don't get is how he remembers it all!

Is this possible?  Does the NETHERLANDS have its own "Yogi Berra"?  :D
Michael Salemi
Davidson, North Carolina (Charlotte Area) USA
1969 280SL (USA-Spec)
Signal Red 568G w/Black Leather (Restored)
2023 Ford Maverick Lariat Hybrid "Area 51"
2022 Ford Escape Hybrid
2023 Ford Escape Hybrid

ja17

  • Full Member
  • Platinum
  • ******
  • USA, OH, Blacklick
  • Posts: 7384
Re: Automatic Transmission Electric Stuff
« Reply #7 on: January 16, 2010, 14:46:50 »
Hello Dan,

Thanks for the kind words.  The one nice thing about this group is there is always something to learn. Even myself have gained much knowledge from the group. New eyes always bring new ways of understanding things and solving problems. Different life experiences allow contributions to be made by many in the group. In some cases people have become engaged in special aspects of these cars and they have become experts in specific areas. Some of you guys are excellent teachers and presenters and contribute by organizing and documenting the information  for us all. Its a winning situation for everyone.

The characters and personalities add a little spice to the learning process and make it even more enjoyable. This is something which is not tech manual or workshop manual.

Of coarse the most difficult thing to perform on these cars is diagnostics. Procedures can be described in detail but diagnostics is where years of experience and good logical thinking really make the difference. This is where experienced experts like yourself and many others perform a most vital service to the group. Some technicians never become good at diagnostics.  Diagnosing problems from long distance, over the internet, is even more challenging. It's like fixing things by remote control (without sight, feel or sound).

My description of "wisdom" is knowledge with good judgement. Wisdom does not come out of a book. Wisdom is gained from experience and knowledge.

Thanks to all the other experts out there for sharing your Wisdom!
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Cees Klumper

  • Full Member
  • Platinum
  • ******
  • USA, CA, De Luz and Los Angeles
  • Posts: 5679
    • http://SL113.org
Re: Automatic Transmission Electric Stuff
« Reply #8 on: January 17, 2010, 09:29:20 »
Is this possible?  Does the NETHERLANDS have its own "Yogi Berra"?  :D

Yes, Johan Cruyff is well known for his statements. Like, when the national Dutch team captain missed two penalties in a critical match, and the reporter asked Johan: "Johan, what is he doing wrong?" to which Johan replied "he is not kicking them into the goal". Or "In order to score, you must have posession of the ball". And "People think I am a faster runner than the others. But in actuality I just leave a little earlier, and that is why I get to the ball before the others". "The Italian's can't win from you, but you CAN lose from them". "Orange (the Dutch national soccer team's color) is a happy color".
Cees Klumper
1969 Mercedes 280 SL automatic
1968 Ford Mustang 302 V8
1961 Alfa Romeo Giulietta Sprint Coupe 1600
1962 FIAT 1500S OSCA convertible
1972 Lancia Fulvia Coupe 1.3
1983 Porsche 944 2.5
1990 Ford Bronco II