Rear Seat Heating Diagram (2005 545i)
 

I wanted to share this wiring diagram so that anyone looking to retrofit rear heated seats in their car can understand how it's done.

I've seen several posts where of people have either asked about it or installed an aftermarket system:

F30 - F30 Rear Heated Seats Retrofit
E53 X5 - General wiring question for aftermarket heated seats
E53 X5 - Heated seat retrofit with pictures - Xoutpost.com
E38 7 Series/E39 5 Series - Heated rear seat RETROFIT kit - E38 / E39
E60 5 Series - BMW Coding Forum
E60 5 Series - https://5series.net/forums/diy-do-yo...trofit-108722/

I performed the retrofit on my 2005 545i which did not come with the seat heating feature ($490). I purchased a set of front & rear seats off ebay for a good price ($1000 shipped). Fronts are comfort with heating & ventilation and the rear seats are heated and fold down. Installing the front seats was easy since they're plug & play. But when it came to figuring out how to wire up the heating for the rear seats I was at a loss, I thought surely there had to be some component of that system that would have been prewired into my car but that wasn't the case at all. Turns out if your car does not come with the rear seat heating option 490 "SEAT HEATING FOR REAR SEATS" then the wiring is not included on your main wiring harness or loom that goes from the front of the car to the back running down both sides. The only part of this system that is installed by the factory is the 2 fuses in the luggage compartment power distribution box (Fuses 54, 62) wow thanks BMW you really went the extra mile.

I wanted the rear seat heating to look and operate as if it came with that option from the factory, using the original switches as it's intended to. I've seen people install an aftermarket system but I don't like how those switches are toggled on and off becuase if you turn them on & leave them on when you shut the car off, the next time you go to start the car it will come back on until you flip the switch to the off position. The OEM system turns off the seat heating when the car turns off, and it will stay off when you turn the car back on later.

I studied the wiring diagram from BMW planet's WDS and figured out exactly where all the wires go, what type of connectors to use and what gauge wire is needed. I put together my own diagram that combines the wiring schematic and pictures of all the locations of the connections. This made it easier for me to understand, as my goal was to construct a wiring harness that mimicked the diagram exactly. If I did construct the wiring harness it would have been expensive and time consuming, but luckily after interrogating and harassing a bunch of sellers on ebay who were parting out E60's I was able to find someone who sold me the main wiring harness completely intact which included the rear seat heating wires. Cost was $50 which is an incredible deal and on top of it the guy was only a 30 minute drive away. I had previously obtained the seat heating switches & rear console panel with the slots for the switches and dark poplar wood trim to match my interior. Total cost for that assembly was $100.

Unfortunately the main wiring harness I bought was from was a 2006 550i with an unknown production date, my car is a 2005 545i with a production date of 10/2004 so there were some differences. The K9 Relay (Terminal 15) is supposed to be located in the luggage compartment for my model year car, however the harness I bought had the relay located above the front fuse box behind the glove compartment so that's where I chose to put the relay. The length of the wires going from the relay to the switches would not have been long enough if I put it in the trunk like it shows in my diagram. Another difference was that my car has both fuses in located in the rear fuse box, while the 2007 E60 has 1 fuse in the front, and the other one in the rear. This diagram is specific to my production date, and I'm not exactly sure how many times the wiring changed throughout the E60's life cycle, I know it changed at least 3 times. One helpful thing I learned was that Pin #4 (Grey & Red Wire) which gives illumination to the switch only needs to connect to any existing grey & red wire on the loom. They are everywhere throughout the main harness so it was easy to find one to connect to I just spliced them together and tapped into the already existing gery/red wire that gives illumination to one of the cigarette outlets. Also when it comes to giving ground to the 2 switches I just wired it to the same ground terminal that the seat heating elements go to, instead of following the diagram because it goes somewhere else out of the way (up by the drives side foot well near the light module).

It seems that rear heated seats are becoming more easily available and more affordable not only for the E60 but for the 3 series & X5's as well, I see them for sale on ebay all the time. I'm sure the wiring diagram varies slightly for each car but the basic concept is the same. There's a good amount of interest in having this so I hope for this to be beneficial to those who want this retrofit. The diagram is in a PDF & a JPEG which I built using excel. The forum wouldn't let me upload it because it's over 5MB so if you're looking to use the excel file just send me a PM. Enjoy!

Diagram
Attachment 150326

Main wiring harness from 2007 550i donor car.
Attachment 150327

Cutting open the wiring harness.
Attachment 150328

X11010 connector that goes into the power distribution box, the top left socket is where you connect the wire that goes to the relay (#5).
Attachment 150329

X11010 connector from the front.
Attachment 150330

X11012 connector that goes to the power distribution box.
Attachment 150331

Universal charger/hands-free kit retrofit connector that I cut out. I cut this out because it takes up space in the rear section of the center console where the switches are mounted. I had lot of extra slack of the wires left over when it got to this part so i needed more room for them. This connector doesn't connect to anything it just comes pre wired in case you want to retrofit a Universal charger/hands-free kit which I have no intention of ever doing.
Attachment 150332

Switches after install. Everything works!
Attachment 150333

Great post! Mine is one of the posts you reference at the beginning.

Sine then, I have moved interior from my 2008 (the seats I did the after market seat heat) with my 2007 which came with factory seat heat. I have been preparing to do the retrofit and found your notes here. Thanks for effort to post it up!

I may be looking to PM you and pick your brain. Looking at an E61 (2010) and it doesn’t have rear seat heat. And I’d love to install it. I think I’ve located a proper donor (2008) so now just have to pull the trigger on the car and then the parts to do it.

thank you very much for this post !
it helped me today to do the same to my X3 e83 2006.
:clap: