Seat harness jacks/looms different than the boneyard seats - PeachParts Mercedes-Benz Forum

cmac2012 · #1 11-18-2019, 10:40 AM

Found these nearly cherry seats at the boneyard on an '83 SD, I think I have the year right, definitely an SD.

I opted to buy both seats, frame and all as my passenger seat performs poorly, not sure if the switch or the seat motors are bad, and removing just the cushion frames has its own difficulty, need to splice the wires for the back, plus I've not removed just those yet, though I think I'm about to learn.

Ran into major buzzkill last night when I found the harness looms are different. Here's the SDL:

Here's the SD:

I see the same colors on the wires in the SD unit, fewer of them of course. Cutting and splicing seems daunting. If I ultimately need to stick with the lower motor frame from the SDL and merely replace the cushions, not sure having Effed with the harness will be all fine and dandy.

I gather the greater complexity is for memory which I have absolutely no interest in. If it still functions I'm not aware of it.

Diseasel300 · #2 11-18-2019, 11:46 AM

The difference in wiring is due to the memory function. The most likely culprit of random or erratic performance of the power seats is the switch in the door. They get gummy and fail to make contact anymore. They can be disassembled and cleaned/lubricated to get perfect operation again, but beware that there are a zillion little springs and dumbbell shaped contact pieces in there!

dieselbenz1 · #3 11-18-2019, 11:52 AM

Those connectors can be opened and wires move around within the connectors. Should be no or little need to cut and splice,

cmac2012 · #4 11-18-2019, 01:59 PM

Quote:

Originally Posted by dieselbenz1

Those connectors can be opened and wires move around within the connectors. Should be no or little need to cut and splice,

There is no way the jack on the SD seats will fit in the female harness loom on the SDL. The pins are smaller and closer together on the SDL. Even the wires are smaller. And I have no way of knowing that if I matched every wire (8 of them) on the SD plug with the same color wires on the SDL that it would work flawlessly.

I've had the thought that I could find each matching color and open them back from the loom w/o cutting them - I've done it many times over the years - shave off about 3/4 to one inch of insulation on the side and carefully work in a tiny screwdriver to make space between the wires and the remaining insulation. That way, if it doesn't work and I end up putting the new leather on the old frames the looms on car floor would still be usable.

cmac2012 · #5 11-18-2019, 02:20 PM

Quote:

Originally Posted by Diseasel300

The difference in wiring is due to the memory function. The most likely culprit of random or erratic performance of the power seats is the switch in the door. They get gummy and fail to make contact anymore. They can be disassembled and cleaned/lubricated to get perfect operation again, but beware that there are a zillion little springs and dumbbell shaped contact pieces in there!

I went off on a semi loopy project to replace the driver side seat switch on my SD back in '06. Used 4 BMW seat switches. I saved it, couldn't bear to part with it. I'm thinking to use it. Clean the switches and splce it in ... if the wiring is the same, no guarantee of that.

Here's the thread:

www.peachparts.com/shopforum/tech-help/143038-w126-seat-switch-replacement-success-4-used-window-switches-work-after-all.html

83w126 · #6 11-18-2019, 10:49 PM

You can't use those motors or frames. Get the seat bases from a later Gen 2 w126 and swap the rest of the parts over (complete back and bottom cover) from the seats you just bought. The 86+ electronics are not interchangeable with the older ones.

cmac2012 · #7 11-21-2019, 06:46 AM

The Vietnamese mechanic I spoke of who is into the 350SD (owns two of them) gave me these seat parts after I paid him $1100 to fix the stalling problem on my van. Had stumped me for years. It's an old van but way useful, would have cost me a lot more than that for a good replacement. He saw my SDL, I told him the seats were lousy, he said I could have this one.

Now I realize I need to ask him what car they came from. Or maybe I could look to see if the same wires on either the SD or the SDL. I have seat samples from both on hand.

Diseasel300 · #8 11-21-2019, 11:32 AM

Without a FSM wiring diagram in front of you, it's a lost cause. Why not transfer the good parts from one seat to the other and not worry about reinventing the wheel? Would be WAY less effort and you'd still have a working seat.

cmac2012 · #9 11-21-2019, 01:10 PM

That does look like the safest route and I suspect I'll go that route. With the parts I now have I'll be forced to do that with at least one of them. I'm not practiced in moving and reattaching the upholstery parts. I think the lower butt part of the seat could be attached with frame intact - no motor or wiring in that one. If I want to leave the upholstery padding on the upper part frame would need to splice wires. For my cowboy ass, easier to splice wires than mess with the skin and flesh parts.

83w126 · #10 11-21-2019, 10:44 PM

The covers are actually really easy to take off, the only hard part is that on the lower cushion, the leather on the sides where the plastic trim covers it up is extremely fragile because there is no reinforcement.

cmac2012 · #11 11-23-2019, 04:26 AM

The plastic trim on the back of the upright looks a tad daunting as well.

It occurs to me that I might be able to sell those seats for $100 apiece. They cost me about $60 each, not much markup but at least I recoup my purchase price. That would hinge partly on me finding good seats out of a gasser 126. I just saw one on the web, a '91 420SEL. It's in San Jose, about 20 miles south of me. I'm also interest because it's white, my color. I could use a rear passenger door, mine got bashed in hard in a parking lot, no ID. Funny thing, the door was all that got hurt and it had a small mark on it already.

To the seats, I hate to admit it, would be easier for me to just bolt in compatible set. Also, he who shall not be named raves about later model 126 seats. Maybe I could find a better style. Comparing the 84 SD seats to my SDL units, I see that HWSNBN's assertion that later seats are more stiff than earlier ones (in a good way) is a selling point. The SD seats I have are sort of too easy to collapse, much more so than my SDL.

ykobayashi · #12 11-23-2019, 10:14 AM

Those seats are beauties. Yeah I second pulling the covers and springs and swapping them to the old frames and motors if you can.

Another possibility is tracing the wiring with a meter and by color and drawing up the wiring diagram. You can power the motors with a battery to see which is which. Then cut and splice the harnesses to mate them into a hybrid. It’ll take a few hours but I’d do it to have those leather seats in my 82 SD.

cmac2012 · #13 11-23-2019, 01:38 PM

I had thought to try to use the entire bottom frame and covering. But I now see it will take an act of God to get that frame off of the SDL seat. In order to experiment with wires, I'm going to need to find a later, post '86 126 and get the mail jack which is wired to the car. The female is under the seat, you can't see it, and the posts are small. Sending current to those would be tough.

This is needed as you need to move the seat mount back and forth to unscrew the seat frame. But even if I pull that off, the older 126 lower frame is just not as beefy as the later version.

The video of seats by he who shall not be named can be found in a search for "Mercedes 126 seats." He points out the more solid spring action on the later seats. I've experienced the weakness of the earlier 126 seats. My long gone '81 300SD had badly worn front seats when I got it. On my rear SDL lower seat, the weakness of the springs was depressing, NPI. I get a kick out of doing road trips with riders from Craigslist rideshare and I sit in the right rear spot when someone else is driving. The legroom in the back is great on the SDL and I can see the gauges from there easily. The seats are still comfy enough but they sag too much. So when I found one with better leather at a boneyard I bought it, and filled the empty voids in the structure with pieces of triple thick cardboard and several sliced up camping pads I had lying about. Much, much nicer seat.

And finally, I removed the back trim of the front passenger seat on my SDL, and whoa, way, way diffrent than the seat back my buddy gave me. The lines look like air, not electric, and they squeeze like air lines. Not sure how they do that. Pretty sure there are also electric lines to the side.

You can see in these two pics the difference in the springs, the first is the SDL, they are both oriented with the leading edge, the part closest to the dash, at the top of the photo:

I think the lower pic, the freebie frame part, is a passenger unit, seems that the broader steel support part is oriented toward the door, perhaps more hefty owing to the passenger weight first landing there.

ROLLGUY · #14 11-23-2019, 07:00 PM

As others have said (I agree), the upholstery and padding (horsehair) is easily removed, and installed on your existing seat frames.

Alec300SD · #15 11-23-2019, 08:10 PM

Quote:

Originally Posted by cmac2012

I think the lower pic, the freebie frame part, is a passenger unit, seems that the broader steel support part is oriented toward the door, perhaps more hefty owing to the passenger weight first landing there.

Use the freebie passenger(?) spring box on your driver's seat.
If it is a passenger spring box, it will have a lot of life left in it, as it is was less often used.

The spring boxes for the front seats are the same for the driver and the passenger.
The late W126 spring box is the firmest, and can be installed on any W116, W123 or W126.
Cylindrical foam inserts are available for front coil seat springs to firm it up a bit more.

I've installed the late W126 spring boxes in my W116s, and posted a DIY years ago.
DIY – Pictorial - W126 Front seat cushions in a W116