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I bought a pair of electric heated seats from eBay, I don’t care so much if the heating works since I live in Cyprus(20 degrees plus in the winter) but what about the electric function, my existing seats are not electric when do I get power from?

I *think* there was a thread about this. You might also want to PM cj10jeeper--he's pretty much the mod master.

Andreas - I previously had electric seats and retrofitted ///M on to the bases so not actually wired when they are not currently there.

All electrics and memory function are contained in the seat so it should just be a case of plugging the new seat connector in, unless BMW have skipped a piece of the loom out. That said I don't know where the user seat setting controlled by the key are stored so ther emay be some dealer programming to code the seats??

With the battery disconnected (else it will set on an airbag alarm if you tun on the ignition) unbolt one of your seats and have a look at the plug. You should see the extra power leads on your new seat running to the controls and motor. If you have matching power on the harness coming out of the floor you're good for a plug in swap. If not then you need an extra piece of loom that I can't help with.

Hope that make sense.

CJ - this is from a manual seat when I took it out during the first satnav retrofit. Is the wireloom similar to yours?

PVR - I can't tell and as luck would have it I've just fitted the drivers side storage box to stop me taking a quick look.
Looking at your picture you'd need to look at the left hand side which is a composite plug and see if there are blanks that correspond to the wiring on the new electric bases that match unusedwires from the loom side. If they are then I guess it's pretty much plug and play

I am lazy as well That car was long ago sold and I can't be bothered to check the underneath of my M

pvr wrote:I am lazy as well That car was long ago sold and I can't be bothered to check the underneath of my M

All cars up to 2005 facelift (not sure after that) had a complete wire loom installed.

Here is a previous post about how to remove your seats...

http://www.z4-forum.com/forum/viewtopic.php?f=12&t=4474

Thanks for all the info guys i just have to wait a couple of days to receive the new seats and we'll find out

mine's a facelift and didn't have the electric pre-wired so i swaped the seat swobs of my new elec/heat/leather over to my standard manual/cloth seat frames.

I was the oppersite not to bothered about the electric adjustment as all the motors weigh more than me - but in need of heating so i'm retro fitting that!

My car has the connector but the wires that give power for heating and the electric functions are missing. So I think I have to put more wires in the connector but I don’t know where the wires end???

Andreas, send me you cars year and what side the steering wheel is on. I will look up the electrical diagrams for the seats for you.

This is how the seat heating works, as described by the BMW WDS V12.


Seat heating
The seat heating system heats the seat cushion area and backrest. The electronics for controlling the selected heating temperature (3 stages) and fault monitoring are integrated in the switching center.

Function
Seat heating can be switched on in three heating stages as from terminal 15 by pressing the button. Three LEDs built into the switching center light to indicate operation. "Terminal 15 active" is signalled to the switching center via the K-bus.

Initially, heating stage 1 is activated when the seat heating is switched on (button pressed once). The seat surface is heated up to approx. 44 °C. All three LEDs light to indicate operation.

By pressing the button once more, the topmost LED goes out and heating stage 2 is activated. The seat is now only heated up to 39 °C.

The seat heating system is switched to heating stage 3 by pressing the button once again. The bottom-most LED lights. The seat is heated up to 35 °C.

The seat heating is switched off by pressing the button once again or switching off the ignition. The seat heating can also be switched off in any heating stage by pressing the push button for longer than 1 second.

The seats are heated by means of carbon fibre heating mats in the main section and steel wires (steel filaments) in the bolster. A carbon fibre heating mat is installed in both the seat cushion section as well as in the backrest. The center sections of the seat and backrest as well as the bolsters of the seat and backrest are always heated. Heating filaments or carbon fibre mats are additionally integrated in the thigh support on sports seats. The seat and backrest bolsters are not heated on the series E39 sports seat with fabric cover.

The temperature is measured by a temperature sensor in the seat upholstery and passed on to switching center.

Monitoring functions
Battery voltage
The electronic seat heating control switches off the power supply to the heating mats if the battery voltage in the vehicle is less than 11.4 V ±0.3 V. The function LEDs however remain on. Power supply to the heating mats is restored when the battery voltage is greater than 12.2 V ±0.3 V for at least 5 seconds.

PC-Board temperature
Due to the fact that the power input of the seat heating system is very high (120 W), the temperature of the pc-board in the switching center is monitored by temperature sensors. Initially, the heating power is reduced as the temperature increases to over 85 °C. The heating is switched off if the pc-board temperature exceeds 95 °C. The function LEDs however remain on. The seat heating cuts in automatically again when the pc-board temperature drops below 85 °C.

Fault monitoring
The electronic seat heating control system monitors the temperature sensor and heating mats for faults. Detected faults are stored in the fault code memory of the switching center.

The following faults can be recognized:

Short-circuit or line break

Short-circuit or line break of temperature sensors

Break in heating mats

If a break or short occurs at the temperature sensor, the seat heating is switched off in order to prevent overheating. The function LEDs are switched off.

Shipkiller wrote:Andreas, send me you cars year and what side the steering wheel is on. I will look up the electrical diagrams for the seats for you.

The year is 12/2004 and its right handed.
Thanks a lot

When I get home tonight (my time), I will post on my website and let you know. The SRS drawings are allready there....