BMW Heated seats

[ssv]

I installed seats from a 2004 330 BMW into my 1969 GTO.
They're heated and I'm trying to figure out how to connect up the heat option.

It has 2 wires related to the heat; when you connect 12 volts to 1 wire (larger gauge) that heats up the seat (low setting). When you connect the other wire (smaller gauge wire) to 12 volts it heats it up to high (both wires are connected to 12 volts at this point); it gets way toooo hot (almost like it's going to burn the leather)....

The question I have is - Has any body used these seats and do they know the correct way to supply power?

Or does anyone have a BMW with heated seats; how do you control the heat? Is it one switch to turn on and another to adjust temp?

I'm wondering if the lower gauge wire gets adjusted voltage, which controls the heat. Guesing 12 volts would be high...??

thanks in advance

[Tiger]

I do not know, but since one wire is thinner I presume that this is to regulate the heat. you could put six volts on the thin wire to se if it lowers the heat.

[barno68]

Not sure on the wiring, but am interested in the install as I am looking to use the same type of seats. I am searching now for either 330 or 335 tan convertable seats as they have the integral seatbelts. Any issue with adapting the rail mounts?

[68byrd]

I am a BMW tech. I can look, but I am pretty sure that the seat heater has a pulse-width modulated power to the heater mat. This is how they have the three different heat settings. There is a module in the vehicle that controls the voltage to the mat.

[ssv]

Brent -
I thought about using convertible seats but did not want to modify the GTO at all, I'm pretty sure the standard mounting is not strong enough to support a seat that has integrated seat belts.

I used coupe seats so they would flip forward to provide rear seat access... My buddy welded metal to the BMW frame rails so they lined up with the standard GM holes. Sorry but I did not take pictures during the process, but I can post pictures of them installed in the car (give me a few days).

The trick was to use the passenger seat for the driver’s side (driver’s for passenger). Some rewiring, dismantling of seat and mounting the controls to the other side and it fits pretty well. Also the seat backs had to be swapped because on the passenger seat it has a ‘flip forward’ release on both sides of the seat; so the driver can flip it forward. The driver’s seat only has a release on the outside.
As always the first one was a bit of pain (not knowing what to do) but the second one was a piece of cake.


68bryd – Any help would he great. If you had the schematic that would be really helpful (I think).

[68byrd]

Sorry, I can't give you a wiring diagram. But the seat mat has a sensor is it that measures the temp of the mat and when the mat reaches the preset temp for the selected setting the control unit backs off on the voltage and keeps the temp where it should be. You might be able to find a diagram on the internet. The control module is not on the seat, its in another part of the vehicle. Sorry I can't be more help.

[barno68]

What was the reason for switching the seats between the passenger and drivers side?

[CarlC]

Maybe you could figure out a way to use a DC Controls or Spal fan control for the pwm/voltage regulation.

[astroracer]

Just a thought here. How often do you drive your goat in freezing weather where you actually need a heated seat? Leaving the heaters disconnected would be fine if you don't really need them...
Mark

[streetk14]

It might be a little bit of work to get them operating properly, but I think it will be worth it. For anybody who hasn't used BMW heated seats before, all I can say is WOW. They get HOT when on full power almost eliminate the need for a heater. I'm not joking. Even if you don't drive the car when it's really cold, it's nice to have the windows down and the seat heaters cranked on a cool day. FWIW, the heaters in my Recaro's don't even come close to the ones in my 335i.

I am a BMW master tech and can give you a quick overview of how
the seat heaters work. Here it goes:

The heaters have 3 stages, stage 1=111 degrees F. Stage 2=102 degrees F. Stage 3=95 degrees F.

There are carbon fiber heating pads that are wired in parallel. The seat base pad also has a temp sensor that provides feedback for temperature control.

These temperatures are maintained by the SZM module (the switch cluster that is located in the center console on the BMW donor car). This control unit monitors the temperature through a NTC (negitive temperature coificent) feedback.

So basically, you have 2 wires to work with. One is the power supply wire from the module and one is the temp feedback to the module. I think you should pick up one of these switch panel modules from the junk yard or ebay. It's pretty small in size and you could mount it in a way that it looks good in the car. Just try to get one that only has the seat heater switches on it. If the car has other options (park distance control, rear sunshade, convertible top, etc.) it will have other switches that will make it not look as clean in your car. Oh, and try to get the electrical connecter with some wiring if you can to make it much easier to hook up. You could buy the connector and some pins from a BMW dealer if you can't rob them from the salvage yard.

I don't think wiring up the module would be too hard. Probably just needs a couple power inputs and a ground to work in your car. I can take a look at the ETMs and let you know.

Andy



I actually found one on ebay. Buy it now for $45: http://cgi.ebay.com/ebaymotors/BMW-E...ayphotohosting

[ssv]

Andy - Thanks and I appreciate any help I can get.

Mark - I really would never drive the car when it's really cold. I love driving in Autumn and with the top down having heated seats is nice. Don't think I would actually buy a heater for seats (in this car), but If I have em why not hook em up...

Brent - Reason why I switched the seats is beacuse the frame rails are offset on the BWM. I guess it could be modified to fit as is, i just found it easier to switch them.

Can't seam to post pictures not sure why?? Can I eamil them to someone to post.

[BonzoHansen]

sign up for an account at photobucket.com so you can post pics.

[ssv]

good idea

http://photobucket.com/ssv

[BonzoHansen]

Nice. I was eyeballing the seats in my mother in laws 07 535Xi. Think she'd notice if they were gone?

[ssv]

Hey Andy

I found this on the web http://forum.e46fanatics.com/showthread.php?t=341242
Does it look right to you? (**My comments**).

I need to get the wiring connector for the back of the module – do you know if BMW sells just that part? If so do you know the part number?

By the way the reason I don’t know the color of the wires and refer to them by gauge size is that the seats are installed and I didn’t right down the wire color. I extended them by gauge size…

From site:
Step 5: I opted not to puchase the OEM BMW retofit kit simple because I wanted a challenge first off, and second I wasn't going to pay ~ $300 for a wiring harness and button panel that I could easily make and obtain. First lets look at Heated Seat Retrofit PDF manual, it gives detailed information on the wirig harness. I read through i and simplified what the harness is all about here is the way I saw it as:

To Passenger seat Side:

B1 - Seat Heating On (GN/YE) - Plug X279 Pin 25 (**larger wire**)
B2 - Ground (BR) - Plug X279 Pin 24
B3 - Temperature (WT/BL) - Plug X279 Pin 23 (**smaller gauge wire**)
B4 - Ground (BR) - Under Pass Side Skirt (B2 <---> B4)

To Driver seat Side:

A1 - Seat Heating On (GN/VI) - Plug X275 Pin 25 (**larger gauge wire**)
A2 - Ground (BR) - Plug X275 Pin 24
A3 - Temperature (WT/GN) - Plug X275 Pin 23 (**smaller gauge wire**)
A4 - Ground (BR) - Under Driver Side Skirt (A2 <---> A4)

To Console Switch:

Passenger Side:

B1.1 - Seat Heating On (GN/YE) - X1869 Pin 1 (B1 <---> B1.1) (**connect to larger gauge wire**)
B3.1 - Temperature (WT/BL) - X1869 Pin 20 (B3 <---> B3.1) (**connect to smaller gauge wire**)

Driver Side:

A1.1 - Seat Heating On (GN/VI) - X1869 Pin 13 (A1 <---> A1.1) (**connect to larger gauge wire**)
A3.1 - Temperature (WT/GN) - X1869 Pin 21 (A3 <---> A3.1) (**connect to smaller gauge wire**)


To Fuse Panel:

C - K-bus (WT/RD/YE) Fuse Box Joint Connector X10116 (Trigger/Accessory Wire) Pin 23 - Console Switch (**connect to acc 12 volts**)
D - Terminal 30 (RD/VI) Fuse Holder A46 slot No. F42 (30 amp) Pin 7 - Console Switch (**connect to battery**)
E - Terminal R (VI/BL) Fuse Holder A47 slot No. F12 (7.5 amp) Pin 22 - on Console Switch (**connect to acc 12 volts**)


thanks
Sonny