Put W126 seats into my W123 - first impressions
 

Well, I've only done the driver seat so far. My car is a 1982 300TD with 324k miles. The car isn't exactly tip-top, but I've done my best to take care of it in the last 10 years, and the PO kept it up nicely. But no amount of diligence could prevent a saggy, squishy, torn, unsupportive driver seat.

I got a pair of seats from a 1986 560SEL, which are the genII w126 seats with full power, heat, and memory. I took the seats with all the control units still mounted to the bottom of them. I cut the wire harness on the bottom of the seats, and took the switches with cut harnesses. I originally wanted to put the switches in the doors, but it didn't look like they'd fit flush anywhere. I ended up putting the switches on the floor right in front of the inner rail, so one has to lean forward and pick up the switch to adjust it (like a manual seat). It's not the most aesthetically pleasing solution, but its elegance lies in its simplicity. No need to run wires through the door jamb, cut door panels, etc. All the wires are color coded for soldering the switch to the seat harness, and I just teed the 12gauge RD/WT and RD/YL to power, and the 12gauge BR wire to a good ground. They will be fused as soon as my fuse holders show up in the mail.

The w126 seat does bolt right into a w123. The holes in the floor pan are in the exact same pattern. I read that one could also detach the rails from the seats and mount a w126 seat onto w123 rails to simplify the wiring (and reduce the weight) but there still needs to be a switch for the recline, and for the headrest (if desired), and of course power and ground. The w123 seats are pretty light for such a large seat, I'd guess 30 lbs each. The w126 seats are massive, I'd guess 80-90 lbs each.

It feels like the w126 seat is higher than the w123 seat. Even when lowered all the way, it won't go as low as the original w123 seat. I kept my w123 seat a little above the lowest height, and now with the w126 seats bottomed out, it's a bit higher than I'm used to but I can acclimate to it. If you have large thighs or are very tall, this might be an issue for you.

I had to use the w123 seat belt rail.

I just found out the w123 seat belt buckle won't work with the w126 receiver, so I either have to take the seat out again and try to put the w123 receiver onto the w126 seat, or else find a way to swap out the buckle on the belt itself. I don't think it will be possible without unstitching the belt end. If anyone knows how to resolve the seat belt issue, I'd love to know!

Oh yeah, and I LOVE this seat! No joke, it makes the whole car feel like it handles and rides better. And of course the fact that it's leather is a plus. :)

Anyway I know it's been done before, but I searched a few forums extensively, and found little documentation on the swap, difficulties, what needs to be modded, etc. so I just wanted to share my experience.

Awesome !

I love the seats in my W126. I think they are much more comfortable than the stock units in my W123. This is so cool. I wonder if you would sit any higher if the W123 base was used with the 126 seat. Meaning, will the seat still drop down as far?

Can you share some pics?

Thanks for sharing.

Hmm, my seats wont raise or lower, but are in REALLY nice shape, as is the rest of the car.

The lever on the side is for the elevation, and the one in the front is for the forward and reverse.


I have the spring box ( seat bottom) out of a 90 W126 to install into a W123. I measured both spring boxes, and they measure the same. The 126 seat out of a Gen II has an additional spring in the front, along with a round dense piece of rubber that fits inside of each corner coil spring in the front.

Iam swapping the 123 tracks to this seat.

Charlie

Any pictures of the done deal?

I took the seat belt receivers off of the w123 and w126 passenger seats to compare. It looks like the w126 seat only works with the w126 bracket, but I can swap over the buckle receiver itself by unbolting it from the bracket. I don't want to cut the wire, so I have to fish the wire out and feed the new one in. Not a huge problem. Every project has a snag, this one's relatively simple.

I was waiting to get the passenger seat installed to take pics - I thought it would look goofy with the fronts mismatched. I'll take pics when I'm all done.

I didn't measure the rails/tracks' height difference on the w123 vs w126 seats to see if the height difference is in the rails or the seat, but charmalu answered that question.

Since the height adjustment is rarely used on w123s, they tend to seize over time. Just try holding the side lever up and rock your weight back and forth. If that doesn't work, you can try some spray lube in the rails (beware, this can/will get messy).

New user here - just registered. New to Mercedes forums in general, but I've been driving older Mercedes since 1996.

I just picked up a 1983 240D with the worst driver's seat I've ever seen.

I wonder if it's possible to remove the W126 electric seat controls and motors and swap the manual controls over to the W126 seat. Anyone have experience doing that?

I thought about swapping out the spare set of W126 seats that I have into the Gwagen but I had some concerns about width and more importantly the weight. Admiral-ahani is correct in his assessment that those seats are HEAVY. The thought of trying to lean them forward for rear seat access didn't come across as very appealing....

Welcome to the forum, :dj:

As I mentioned in post#4, I used a passenger side seat bottom spring box assy, out of a second generation W126 (86-91) 90 SEL. It is the same size as the one used in the W123. plus it is a up grade with an added spring in the front and the rubber corner inserts. be sure to use a pass side seat on your drivers side, usually the pass side will be like new, and the left side will now be the driver side that gets the most use.
http://www.peachparts.com/shopforum/mercedes-parts-reference-library/183654-1269142215-w123-w126-front-seat-foam-support-inserts.html


Remove the seat back and electric seat rails. then use the manual seat rails from your w123. Be verrrry gentle removing the plastic side dress up pieces, they break easily.

I use a 14.4V De Walt battery and a set of Harbor freight Digital volt meter leads. cut the ends and soldered on ends to fit the battery. then use it to move the seat motors to access the bolts for removal. works good on moving windows and checking a blower motor etc.... look for their sales flyier in magazines, sometimes have the meters for free. :D

Be sure to take pictures as you take the seat rails apart, so you know how to put it all back together. I have taken several apart, but there is always,"now which way did this piece go" :confused:
I know these 126 seats fit, just did this 2 wks ago on the kitchen floor till 2am. the seat now lives in a 82 240D.


Charlie

What about seats out of a SEC? they lean forward for rear seat access.

Charlie

I was thinking the same thing but in the end I just had the original seats reupholstered.

Bump for pictures!

Carmalu. Thanks for sharing. This is awesome. This makes for a much better option to retain manual 123 seat adjust and improve seat bottom.

Magic bus: Welcome.

Thanks for the replies. My post may have been premature. Looks like I may have found a half decent set of palomino W123 seats locally. I'll know more in a couple of days.

Two things:

1. Did the w126 seats decrease the headroom? My impression is that the bases are a bit higher.

2. I'm echoing the call for pics :D!!