[jamieson]

Howdy,

I am building a '73 Dodge Challenger hot rod. Because I value my spine, I bought a set of '03 BMW 745Li seats instead of using OEM style seats.

Now I'm trying to figure out the simplest way to operate the seat controls; I have the center console with all of the seat adjustment buttons. However, I cannot figure out how the seat control wiring is connected to each seat.

I found a link to some wiring information which has been very helpful (http://spaghetticoder.org/bmw/wds/). The front seat controls have wiring ribbons that attach to a small computer inside the console. According to that link, that computer is called the "BZM", its seems that the BZM needs to connect to the "CAN BUS" (not positive what that is) and that in turn operates the seat motors.

Each of my front seats has computers mounted underneath it. I have wiring connectors with pigtails for all of the computer connections but do not know where they connect when they leave the seat.

Basically, I am looking for the simplest way to make the seat controls function outside of the original car.


If anyone has ANY tidbits of relevant information I would be very appreciative. If anyone can give me a solution that I can get to work, it's a pay(pal)ing job.

Thanks!!
Joe

[Old Fool]

Id like to help you but I cannot even see a schematic on the website you link to. I go thru the tree and find the seat, then click it and it wants to download something abut it asks what i wnat to read the file with. I gave up. Prolly something simple but this old coot ant figure it out.

[jamieson]

Thanks for taking the time to look! Most of the files in that link do not work for me either. However, in most trees there are a few files with a different icon (usually at the bottom of the list) that are just text files that explain how things are put together. I got the information I posted about from one of those text files in the seats tree. I definitely wish I could see the other schematics.

[Coodeville]

This sounds more like an electrical question than an interior question. Did you try posting on that board?

[Old Fool]

Here is the 411 as this old fool sees it, the seats you have are memory seats, which are controlled by a computer on the cars canbus. What you need is the electrical schematic of the seat wiring to determine which wires actually run the vaious power motors. There will be numerous wires that tell the computer the location that each of the motors was in when the program sequence was initiated.
You can get these schematics online if you wish to pay for them, or maybe your Beemer service dept would make you photo copies. (highly unlikely from my experiance with bimmer 'tudes)
I purchased a subscription online to the full manual for a Tahoe for a year for around $20. I saved to disc all the info I wanted and let the subscription expire..

You mght find the info you need here:
http://www.automotix.net/autorepair/...45li&year=2003

[sparkydog]

I have not seen what the BMW seat motors look like, but if (IF) it is obvious which wires are power wires into those motors and which are feedback or "encoder" wires for the seat positions, then maybe you could proceed with simple power up of each wire to learn which motor and which direction they drive.

[DanTwoLakes]

Let's put this in Electrical.

Dan

[jamieson]

Thanks, definitely should have stuck this in electrical.

Thanks for the replies everyone; I will continue searching for wiring schematics.

I attached a picture of the computers and wiring underneath the seat for clarity.

[jamieson]

I just now registered at the website that Old Fool suggested. It cost me just a few bucks for 7 days and looks like it has a ton of useful information.

I am decent at electrical work on classic cars, but modern BMW electrical is much more complex.

The attached wiring diagram makes it look pretty simple, but the whole can bus thing is new to me, so it is going to take some research to do it right. I still haven't found where this system gets battery power from... back to study diagrams.

Thanks for the help!

[EOD Guy]

My 2 cents..... The BMW has a memory function for each key...... my key puts the seat where I normally have it when I enter the car and insert the key and does the same when my wife puts hers in etc... That part will be extremly hard to duplicate due to the BMW using a security/controller computer (it actually has one of those 3 letter abrv ) anyway those computers are coded by BMW and provide the movement to the seats via the canbus and are almost impossible to bypass.

You should also have a seat occupancy box under the pass seat that tells the computer to turn on/off the pass side airbag depending if someone is sitting in the seat etc.. There is also a gismo that looks like a metal tube bolted to the seatbelt mech..... that is the tensioner that uses a pyrotechic squib to lock the seatbelt in case of a crash..... be careful with that. Depending if there a seat heaters you will also have a connector for that. My seats have three motors in the frt up/down, front-back, and rear up/down.

[jamieson]

Thanks! That type of information is extremely helpful.

[vicrod]

You also can control the seat motors using relays. Each motor requires (2) relays. The control wiring and switches will need very little space.
See attached diagram.
Typically each motor will have a self resetting circuit breaker to protect it in case the control does not stop it at the end of it's travel.
If you have the room to run the wire, #14 minimum, you can use a double pole double throw center off momentary switch (1) for each motor.

vicrod

[EOD Guy]

I'll try and look in the am for an extra set of motorized bases that I have for my Z3..... I'm pretty sure they have the switches mounted external of the seat, on the plastic trim, and have no computer controling them..... if they are, then you could consideer purchasing a set like them from a eariler BMW and grafting them to your new seats. My 06 X5 has all the compter controlled junk on them etc.....

[ogre]

cut all the wires, toss all the electronics bs
keep all the 1 & 3 wires that feed the motors
get a standard electric seat switch and wire them in
most seat switches are a combination a regular switches
hooked together with a long plastic knob

seat switches are like window switches
2 wires in, 2 wires out
some have 3 in but 2 are grounds
you should not need relays if you use seat switches

[EOD Guy]

the 98 BMW Z3 pwr seats have one knob that raises, lowers, fwd and back and is connected to the motors via a pig tail. Should be an easy graft onto your seats.