Swapped seats from a E320 into my 87 300TD

[johnscars]

Done! I've wanted new 124 seats as mine have 293k miles of butt-compression. I've longed for modern seats to replace the originals with old-school soft spring action. And it turns out one of my seat springs was broken.

2 weeks ago I found a nice pair of modern seats on an E320 at a local junk yard - good lumbar lower back support and firm seat bolsters, got the VIN and asked this forum and MB dealer about compatibility...not...responses cited wiring diagrams showing that the electronics/wiring are different.

But back at the junkyard I decided to sit and look again, the passenger seat was easily accessible and I looked under the seat to see it looked like my 87's electrics/mech. So I negotiated the deal and swapped the passenger seat. It plugged right in, the chassis wiring and electronics matched. plug and play! Unfortunately that is where the easy fun ended.

I pulled the driver seat and stuffed it into the back with my old pass seat and drove home.

Chilo at the junk yard said the seats were not compatible because the new 124 seats have a "brain" - meaning 2 position memory. I said mine has memory, too. But it turns out the main long wiring harness plugs did not align. A 124 expert at the local MB dealership said that given the choice between dismantling the seats and swapping seat chassis, he'd get the wiring harness ($190 new) at the junk yard cheap. I went back to the yard and got it - as much fun as pulling veins from a dead rhino! I seriously doubted my ability to stuff it into my car - and into the door to the new seat controller. (Note: for sale - driver's side seat harness, cheap.) I also got the driver's seatbelt - great move as mine was no longer a competent recoiler, and the back of the belt clip had broken, so the clip fell to the floor...also Note: it needed some old seat-pillar parts swapped in, but it works great.)

Anyway, I went back to the basics and followed earlier advice from Sixto and Dave (Gsxr of 124 SportLine seat fame) to consider remounting the seats on my old seat chassis. First I butchered the old passenger seat to see how it went together. Note: before removing your seat, raise seat all the way, and run it forward (exposing the brass colored philips or torx screw on the front of each side. This screw is at the front of each side and screws up from the chassis into the bottom of the black tubular seat-bottom.) The seat-chassis and the seat-back are bolted to the seat-bottom by just 4 (13mm) brass bolts and 2 phillips or torx screws. But since I didn't run the old passenger seat fwd, the screw was not accessible (Milwaukee Sawsall with "The Torch" hacksaw blades took out the screw top, then "pop" the chassis off with a hammer and a screwdriver/chisel.), then clip some zip ties and stare at the fallen parts. Traced wires, drew a wiring diagram, I also "opened" the seat-back and the seat-bottom to see what is inside, how it is built, how it can be amended (to "open" the leather, use a screwdriver to pry out the leather/metal edge - every 2 inches - and then push down and hold (compress) the seat and pull out the leather edge (needlenose/screwdriver/fingers). Easier said than done - my hands feel worked!) Then I got up my courage and did the same to the "new" E320 driver seat. Sawsall, grinder and dremel, clip zips, traced wires, drew diagram. That is when I noticed that the seat-back of the E320's main plugs were identical (same big wire-plugs and small wire-plugs in the same plug array) to 2 on my old 300 - but the wires' colors were different. There were also smaller wire-plugs for the telephone and for the headrest.) I'll try uploading a photo to show where these 2 main seat-back plugs go (middle of the E320 chassis wiring area, the #1 and #2 of 5 internal plugs.)

So going "all in", I unplugged (from the front) my old driver's seat (remember adjust seat fwd and up), and unbolted (10mm ratchet, from the back go inside through the chassis frame), then unscrewed the 6 screws/bolts, and clipped the zip ties. Then I plugged in the big E320's 2 large seat's seat-back plugs into the old 300 driver's seat chassis, rebolted (2 screws and 4 bolts) the new seat-bottom and new seat-back to the old chassis. Stuffed it into the car, and plugged in the car's 3 big front wiring plugs. Hit the door controls and... "It's alive!" Bolted them down (be sure to attach the plastic side skirts first, careful not to break their brittle bits). All with no wire splicing!

Headrests didn't previously work, still don't. but everything else does, and I'm really liking the new comfort ride! While I had the seat-bottom off, I stuffed a firm wad of closed cell foam under the front (to bolster my thighs) giving my long legs great support on long rides.

I also got the new driver's armrest (removed phone to make storage space) and I got the center console wood (needs hole cut out for front/back stereo controller), and the wood-slat-topped closing box. My wife insists all these are projects for later...
Later...