Electrical Connections on 280Sl Transmission?

[Tom Colitt]

Hi

Does anyone know the exact way to connect the wiring at the terminal block of a 280Sl automatic transmission? There is nothing in the BBB manual and I suspect mine is not all right. Specifically I only have one wire that connects the two small oil pressure switches to each other, left and right of the front of the transmission (they look like little solenoids and have one center mounted knurled thumb nut that holds the wire's cable end in place. I'm pretty sure that at least one wire of the main transmission wiring harness must also connect to the oil pressure switch by the terminal block, but I do not know which one since they are all connected to the terminal block right now.

Does anyone know what color wire goes to the switch?

Thanks a lot,

Tom Colitt

Tom Colitt

[Tom]

Tom,

This website has what you seek.  If you have additional questions, there is an email address at the top of the page.

http://www.mercedesdismantlers.com/16BoltInstallationInstructions.html

Best,

Tom


____________________________________

1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
____________________________________

[Tom Colitt]

Thanks Tom

Although at first glance I see that a green wire with an orange stripe should be connected to the left pressure switch, also a second wire that connects it to the second pressure switch. However, the written instructions (point no. 2.) say that 3 wires should be connected to the left pressure switch.

Maybe it will all become clearer when I actually have the car in front of me.

Regards, Tom

Tom Colitt

[knirk]

Hello
This is maybe written in the text link, but since I just worked on the system here I go: The two oil pressure switches, one for reverse and one for forward gears, completes the circuit to power the little solenoid you have on top of the manifoil.

This solenoid will also engage when the A/C is switched on. The reason is to increase the idle rpm when load demand would lower it. My reverse oil pressure switch was broken resulting in the engine dying when I selected reverse. There should only be one cable from the right switch over to the left, because any of the two can complete the circuit.

Per G. Birkeland
69 280 sl aut 834
Norway

[Tom Colitt]

Thanks Per

So it seems that the Green/ Orange wire is the only wire to connect to the left hand side pressure switch, asid from the wire that connects the two pil pressure switches.

Regards, Tom

quote:Originally posted by knirk

Hello
This is maybe written in the text link, but since I just worked on the system here I go: The two oil pressure switches, one for reverse and one for forward gears, completes the circuit to power the little solenoid you have on top of the manifoil.

This solenoid will also engage when the A/C is switched on. The reason is to increase the idle rpm when load demand would lower it. My reverse oil pressure switch was broken resulting in the engine dying when I selected reverse. There should only be one cable from the right switch over to the left, because any of the two can complete the circuit.

Per G. Birkeland
69 280 sl aut 834
Norway

Tom Colitt

[Tom Colitt]

I just checked the wiring on my 1970 280Sl. It appears to be very original and has the following wiring, similar to but not quite the same as pointed out in the SunValley Mercedes Tech bulletin.

I have 2 brown/white and one white wire with small eyelets going to the small terminal screw.

I have 2 brown/ black wires and one black wire with medium eyelets going to the  medium terminal screw.

The large terminal screw has two eyelets, one containing two brown wires, the other is Black, rather than brown as the bulletin says.

All of these wires come from two harnesses that feed through a rubber grommet in the floor pan just near the kick down switch and leading towards the fuse box. The other harness leads towards the top of the transmission (presumably the double acting solenoid).

I don't have a green/red wire at all.
How is this wire supposed to come down from the fast idle solenoid. Is it a single wire of part of a harness from somewhere.

What does this wire do? Does it merely increase the idle speed when the transmission is either in the forward or reverse gears?

Regards, Tom

Tom Colitt

[Tom]

Here is a picture of my terminal block at the transmission.  My idle increase solenoid is wired to the neutral safety switch.  I understand that it is supposed to be wired to the pressure switch, but I understand that one of the terminals to the neutral safety switch is connected to the pressure switch.  My solenoid activates when the car is placed in gear.

Download Attachment: trannywiring.JPG
58.28 KB

____________________________________

1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
____________________________________

[Tom Colitt]

Thanks again Tom

My terminal block and wiring looks just like yours, except that the small screw terminal has an additional black/white wire going to it (total of 3 wires just like the medium terminal.

It looks like I may be missing the GReen/Orange wire, but by now I've learned enough to know that that is probably not the cause of my transmission slipping, only during the first 1 or 2 minutes.

I've tried adjusting the brake band, replaced and adjusted the modulator diaphram, replaced the primary pump seal, but still no luck. Well, I just have to keep on eliminating things until I find the problem.

Thanks, Tom

quote:Originally posted by Tom

Here is a picture of my terminal block at the transmission.  My idle increase solenoid is wired to the neutral safety switch.  I understand that it is supposed to be wired to the pressure switch, but I understand that one of the terminals to the neutral safety switch is connected to the pressure switch.  My solenoid activates when the car is placed in gear.

Download Attachment: trannywiring.JPG
58.28 KB

____________________________________

1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
____________________________________

Tom Colitt

[Cees Klumper]

Here's some information from older posts on how to check the operation of the three-position solenoid on the auto transmission:

"The usual problem with rough downshifting automatics in these 113's is non-functioning or mal-adjusted three position solenoids or linkages. Oftentimes the intake butterfly stop screw is mistakenly used as an idle adjustment scew. If this happens the transmission solenoid switch on the intake is thrown out of adjustment causing the three position solenoid on the transmission to not function properly or not function at all. This solenoid should soften that last downshift when working properly."

"Joe Alexander: You can remove the access cover on the passenger side tunnel area and observe the movement of the transmission linkage and three position solenoid, while test driving the car. You will need a second person and a flashlight. The kickdown or passing gear switch on the floor under the accelerator pedal must be engaged and working to activate the solenoid. When fully depressed this switch is engaged and it energizes the three position solenoid which will move the control pressure linkage on the side of the transmission. This linkage changes the control pressure at the modulator assembly on the transmission and causes the downshift. Make sure you have power going in and out of the accelerator kickdown switch when it is depressed. Next try observing the operation of the three position solenoid. Position one at idle in gear, position two after driving off, position three at full throttle (accelerator fully depressed and switch engaged). If all seems to be working ok then more complicated adjustments can be made at the modulator or the linkage on the transmission (do this only as last resort and after everything else is checked out). Be sure to check the switch on the venturi. It is a brown bakelite switch with two wires going to it. It is mounted on the intake venturi,a little further up from the air cleaner. With the ignition on, car in gear, the switch should have power at both wires (closed switch). After slightly moving the throttle open the switch has power at only one wire (open switch). Your transmission will never shift right unless this factory setting is restored."

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[tuultyme]

I checked my electrical connection last night on my 1970 A/T.  Mine is wired as is Tom Colitt except that 2 brown/white and one white with medium eyelets go to the medium terminal.   2 brown/black wires and one black with small eyelets go to the small terminal.  This should not make a difference.  I detect electrical power to these wires with ignition on (engine not running) but as soon as I move the accelerator linkage which also causes the idle throttle switch on the venturi control unit to break its circuit there is no longer any power to these wires.  I did not test them with the engine running. Can anyone explain to me what is happening here?  I need to again test that the kick down switch is working as I recently readjusted the throttle switch as I believe this is also related. :?:
Also I have a green/red wire connecting the constant speed solenoid{CSS} with the left transmission pressure switch which is turn connected to the right transmission pressure switch. As Per said either one of these switches will complete the circuit to the {CSS} when the car is in gear.  My {CSS} is activated all the time the engine is running even when not in gear. Could one of these pressure switches be stuck closed causing this problem and how would I test/replace them?  To further complicate the situation in the 70-71 emission control system these pressure switches should be connected to the relay box.  Am I missing this extra wire as indicated in the SunValley bulletin which is effecting the functionality of the speed relay switch?

Bruce; 268Blaugrun(green) 1970 280SL; IL

[ja17]

Hello Guys,
The ring terminals on the wiring and the terminal block screws are different diameters. Pay attention to the sizes and this will help guide you. I have a diagram somewhere also, I will try to dig it up.

Joe Alexander
Blacklick, Ohio

[tuultyme]

Can someone help me in figuring out my transmission pressure switches.  They appear to be giving me a ground to the constant speed solenoid at all times the engine is running not just when it is in forward or reverse gears.  Are these adjustable and how do you adjust them?  There does not appear to be any other grounding of the wire between the constant speed solenoid and the transmission pressure switches so I am guessing that the problem is in the pressure switches.

Bruce; 268Blaugrun(green) 1970 280SL; IL

[knirk]

Bruce,

The pressure switches are only on - off switches. One will ground the circuit when reverse is selected and the other one when forward is selected (I don't remember which side is which). The grounding wire is connected in series from the right switch via the left and to the constant speed solenoid.

You can check them by disconnecting the wire at the pressure switch connection, and measure at the connection for grounding when you put the car in rev or fwd (the engine must be running).

Since you have the idle increase always, I would suspect a ground fault somwhere after the pressure switches.

Per G. Birkeland
69 280 sl aut 834
Norway

[tuultyme]

I disconnected the wires from both transmission pressure switches and found that this wire was grounding to something along its length as it goes over the transmission.  I tried to remove it but it is wedged under something near the top of the transmission.  I suppose a PO or mechanic did this during some repair. This wire is not connected to anything at the top of the transmission is it?  I made up a new wire and ran it over the transmission and reconnected the ends to the switches; now the constant speed relay functions only when the transmission is in gear.  
Should these pressure switches be connected some how to the relay box for the emission control system in an 70-71 car?. Am I missing this extra wire as indicated in the SunValley bulletin which is effecting the functionality of the speed relay switch.  Tom also said that in his 71 one of the terminals of the neutral safety switch is connected to the pressure switch. Is this only in the 71's?

Bruce; 268Blaugrun(green) 1970 280SL; IL