The driver's side seat is in and it works great. There were two female connections plugs on the body. One was square with large wires and matched up with the 'new,' seat from an 84 420 SEL. The other body connector had the same size holes as the seat but there were less holes than the seat's connector. I used the seat's female plug and charted the locations of the wires to match the seat by examination of the seat switch on the door.

The passenger's seat is another beast.

The connector on the left of the photo attachments is original wiring in the body. The other came from the the '86 420 SEL's seat. The seat also had a square connector like the driver's side seat and body connector which the passenger's side body does not have.

Any chance splicing the wires will make the motors work?

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I am guessing that there is an issue because of memory seating. (some seat shave it, some not)

I am working on my seats right now actually since my memory seating is not working.

You can tinker in this:
Mercedes-Benz 126 Service Manual Library

While for a 91 560, it may help a little.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

The memory wires from the seat controls to the connector under the seat are brown, brown w/ rust stripe and brown w/ black stripe the 86 420 SEL.

They are black with the same stripes on the 84 SD.

I'm sorry I don't know whether the memory is in the switch or the seat on either car. If the wiring is correct then the problem must be in the memory, it seems. I haven't a clue here.

May as wel keep this in this thread instead of mine. Do you have memory seating in the controls? They will have a green button with a 1 and 2 button next to that.

If you do not have this in the door, then wiring is not too hard. Based on you pics, it looks like you do not. Otherwise this would be a plug an play.

I can help you match up colors or wires to get you were you need to be. If the seat has a memory module, you can probably remove it (and ship to me!!!). You will have to create a few male ends and such (link in other thread about doing swap). But I can get you dialed in with colors and maybe even tell you exactly what wire goes where. The seat itself, if it has memory, will have many plugs. But of each motor plug you will only need two wires. The other three are used for the potentiometer that read the motor position. That resistance reading of the pot tells the brain box where the motor is and were to return to when a memory function is called.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Either the seats I am putting in this car or the ones I took out have a memory module. You send me a photo of one and I'll find it and send it to you. I don't care about memory function for my passengers. I don't transport anyone in my car often enough to allow them to get familiar. With the car, of course.

Well let me know which way it is. If you have memory function on the door or not is the important part. Cause then I can tell you how to wire it.

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Did Thayer bypass the black control box pictured in the second photo?

Passenger's side:

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Yup, he did. Hence the extra wires.

The controller and box you posted is for memory seating. Without memory the wires go direct from controls to motors. With it they all end up in this box. Thats the box I keep burning up for some reason. You can wiring it either way then, but if the controller was in the seat you installed then this should have been a plug an play since you have memory functions on the controllers. Not sure why the plugs are different.

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

It was strange to me that the 84's driver's side had the small female/male connectors while the passenger side had the larger ones. Thus, my problem here. Never-the-less, it seems you have solved it for me. It appears the motor wires are long enough to reach the connection point and with my disregard for the memory function I expect this to be easy.

If you want the 'brain,' out of this seat I will send it to you. I am surprised someone here has not given suggestions as to why your's was damaged. I have thoughts about this but you seem to be light years ahead of me on seat problems. Thanks.

Dan

Dan, I think my brain box is simply faulty which is why its burning it self up. But I dont want to swap with driver side in case I am wrong! Then I would have two dead boxes. I am working on the seats some more today. I "fixed" my box so I can at least get the seat adjusted a little. At least these seats are easy to remove and install!

I think you figured out how you can wire it. The wires should even be the same color from what I have found. You will just have to tuck&tape the potentiometer wires, the small ones, since they will not be needed. I would not cut anything just in case that seat ends up in someone else's hands in the future.

Good luck!

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

this again. The seat springs are in perfect shape and the leather is strong and pliable. I have drenched the seats in mink oil after a good saddle soap bath. I'll cover them with the sheep skins and live with what I have. Thanks for holding my hand through this.

I'm going to bolt the seat in now.

Just got my passenger seat back in. The repairs on the brain box are working, but I am not operating reverse for more than a split second. Last couple times if I did it would burn up again. But now I can operate the seat properly. Another day will have to be for memory seating.

Fun times, huh?

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Is there any chance of an obstruction in the track of that seat? I know it sounds insulting but I confess I had a screw loose in the old seat and it squalled like a goat. It was between the rollers that can't be seen unless the seat us upside down. Evidently the rear roller moved it forward without much noise but the front roller made all the racket.

I didn't figure out the problem until I bought the 'new,' seats.

Luck!

Nope. The seat will track back and forward fine, just cant hold the button to make it go back for more than a bit or it may burn up something.

On the bench I can apply power to the motor and it goes forward and back without issue for a full run and the amp draw is the same. So I am not sure were the problem exactly is. Last place it to look at the switches, again. Seems like something is short circuiting out, grounding out.

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Any chance that switch is sending two signals?