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Thread: 540 sport seat swap into 525ix - guidance please

  1. #26
    Join Date
    Feb 2008
    Location
    Calgary, AB, Canada
    Posts
    1,811
    My Cars
    BMW 850, Alpina B10 Biturbo, Alpina B12 5.0
    Quote Originally Posted by ross1 View Post
    No intermediate harness without memory.
    Rob, If you need a seat motor let me know I have a couple I think are same.
    Hey Ross! Thanks for the offer. I’m not entirely sure how to test the motor for functionality but honestly it’s not a big concern for me at this point in time. If ambition strikes me again in the future to chase it, I’ll hit you up if that ends up being the issue. My thinking is it’s either got to be the motor and/or the module.

    Cheers and hope you and your loved ones are safe and healthy.

    The kids:
    Alpinas: 91 E34 B10 Biturbo; 91 E32 B12 5.0; 91 E34 B10 3.0 Allrad (mom's car); '91 B10 3.5
    Bimmers: 91 E31 850; 93 E34 525i w/ aftermarket turbo; '01 X5 4.4; 93 E31 850i Dinan TT; 89 E32 750il Dinan TT; 92 750il w/ S70 engine and transmission
    Mercedes: 92 600sel; 93 S600 Lorinser
    VW: 04 Jetta GLS TDI

  2. #27
    Join Date
    Feb 2008
    Location
    Calgary, AB, Canada
    Posts
    1,811
    My Cars
    BMW 850, Alpina B10 Biturbo, Alpina B12 5.0
    Quote Originally Posted by Singing6 View Post
    Quick idiot check: the xdrive and non-xdrive seats are compatible correct? I know there is a bulge into the cabin from the trans tunnel for the transfer case. And I know it is big enough that the floor mats for the Xdrive cars are different. In theory that means the differences are forward of the seat, but thought I would bring it up.
    That is a very good question to ask. To date, the sport seats have not been installed as I’m waiting for delivery of a pin removal tool to properly build the wire harnesses. That said, I have installed the passenger seat from my 525i Canadian spec parts car and it bolted directly in without issue. So, I’m assuming these 540i Canadian spec sport seats will also fit without issue. I will certainly report back if it turns out that there are fitment issues!

    The kids:
    Alpinas: 91 E34 B10 Biturbo; 91 E32 B12 5.0; 91 E34 B10 3.0 Allrad (mom's car); '91 B10 3.5
    Bimmers: 91 E31 850; 93 E34 525i w/ aftermarket turbo; '01 X5 4.4; 93 E31 850i Dinan TT; 89 E32 750il Dinan TT; 92 750il w/ S70 engine and transmission
    Mercedes: 92 600sel; 93 S600 Lorinser
    VW: 04 Jetta GLS TDI

  3. #28
    Join Date
    Oct 2004
    Location
    Monkton, MD
    Posts
    822
    My Cars
    1995 E34 S52, 2013 X5d
    Has anyone in recent years attempted this? I've got a similar situation, 1995 540i memory sport driver's seat into 1995 525i with no memory. When I power the "fat" red/yellow wire in the 4-pin harness and ground the "fat" brown ground, the memory button blinks. If I ground both the fat and the skinny brown/orange, the memory module "clicks" but the seat controls (up/down and forward back) don't respond. I'm bench testing outside the car.

    Could my memory module be dead? Or the seat switches?

  4. #29
    Join Date
    Oct 2004
    Location
    Monkton, MD
    Posts
    822
    My Cars
    1995 E34 S52, 2013 X5d
    Quote Originally Posted by mcw323is View Post
    Has anyone in recent years attempted this? I've got a similar situation, 1995 540i memory sport driver's seat into 1995 525i with no memory. When I power the "fat" red/yellow wire in the 4-pin harness and ground the "fat" brown ground, the memory button blinks. If I ground both the fat and the skinny brown/orange, the memory module "clicks" but the seat controls (up/down and forward back) don't respond. I'm bench testing outside the car.

    Could my memory module be dead? Or the seat switches?
    Update to my own comment: I was previously testing both seats with an 18v drill battery. It allowed the passenger seat to move outside the car but not the driver seat. I read more closely this link:

    https://www.mye28.com/viewtopic.php?...05f50&start=75

    and ordered a Pyramid regulated power supply (PS9KX) from Amazon and tested the driver's seat using the same 3 wires on the memory module that was used in the above 2013 mye28 post and the seat functions properly. So I think I just was not giving it enough power.

    So I can confirm that on the memory module you need constant power to the fatter red/yellow wire and ground to the fatter brown and skinny brown/orange wires. Everything works but the leg extension.

    Is there anyone out there who remembers what wires they tapped to get the thigh bolster working? Could it in theory be connected to the same 12v always-on wire that lets the seat move back and forth?

    I plan to document all of this at some point with pictures since there isn't really a comprehensive post that does this without the intermediate wiring harness which I can't for the life of me find.
    Last edited by mcw323is; 11-21-2023 at 09:19 AM.

  5. #30
    Join Date
    Oct 2004
    Location
    Monkton, MD
    Posts
    822
    My Cars
    1995 E34 S52, 2013 X5d
    So I can confirm that on a late model E34 (1995 for sure, likely 1994+), the memory sport driver's seat thigh extension motor is here, circled in red:

    thigh bolster motor.jpg

    The motor is fed by a yellow/grey and blue/green wire. If you have a tabletop power supply, you can connect a + lead and - lead to the posts in the top connector (that goes up into the metal frame) and see if the motor works. If your thigh bolster is currently retracted inward, i.e. not extended fully, you can connect the + lead to the blue/green wire and the - to the yellow/grey wire and it will make the motor extend the thigh bolster. Obviously the inverse then, + to yellow/grey - to blue green will make it retract. If you are able to do this, your motor is in good shape, which is huge news because its really buried up under all of the front wiring connections and the cable driven motors that are prone to twist.

    Unfortunately I learned through this process that my thigh bolster switch is broken. I also learned that it is now NLA from BMW. I checked with Turner, my local BMW dealer, and even Schmeidmann. From what I can tell a lumbar switch may also offer the same function as it is also a on-off-on momentary switch. I ordered one on ebay (used) and will report back if it works. If not, I've found a plain black switch on Amazon that I will try and make work since the original is NLA.

    Hope this helps someone out there! Getting closer to installing the seats!!!

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