For that rare fellow who would like to add factory heated seats. It can be done. First you must acquire the heated seats. My car is a 2007 GT3. I was able to, when a Rennlist member put his nearly new ones up for sale on that forum. He was replacing them with the GT2 seats in his 2010 GT3.
Next you need the HVAC Climate Control Unit. Part # 997 653 111 14 (Note the last digit can be 1,2,3,or 4. 4 was the most recent update.) These can be found used on ebay and other internet sites, as well as new from a dealer. I used Sunset Porsche.

I swapped out the seats and the control unit myself. Directions for those steps can be found on other posts. Planet 9 has a good article on PCM install that shows the Climate Control Unit removal.
The wiring harness for the heated seats connects exactly like my non heated seats did. The only problem: no wire was present to connect seat heaters to Climate Control Unit . My pals at Harper Porsche, the Knoxville dealership came through with the solution. A wire was ran directly from the Climate Control Unit to the seats, under the carpet of course. The final challenge was the wire connection. Jason, a Porsche Service Tech did a lot of research. This is the Gem of this Mod. Those connectors are a BMW part. Jason tracked them down and eventually acquired some. 30 cents each. Originally used in an older M3. (This has to be an abomination of some kind!) Hardwiring is an option but he was reluctant to go this way.
I picked up the car today. The outside temp was 38 degrees. The heated seats worked great! Toasty buns.
Thanks to:
Chromium 24
Jeff Clark Sunset Porsche Parts.
At Harper Porsche Mark Nagle Service Rep, Jerod DeJong Porsche Tech, and Kudos to Jason Yueng Porsche Tech.

 

This is a very laborious and detailed DIY, I just finished it on a Cayman, same wiring, connectors etc. I addes the factory heating elements. Rough cost is $1000 for and option that is likely $250 from factory.

 

I would like to speak with you about this. What would be the best way?

thanks, travis 503-308-8443

 

1) What is the best under the carpet route for the new harness from the HVAC to the seats?
2) Do you need a new fuse, or do you have to change fuses?
3) Where is the seat heater relay located? Anyone with pics?
4) Does one have to reprogram the new HVAC control with PIWIS?

 

Hi, I am intending to do this also, your post is very helpful but unfortunately I cannot read the part numbers on your diagram, please could you message back with them. Many thanks.

 

HVAC Climate Control Unit. Part # 997 653 111 14 (Note the last digit can be 1,2,3,or 4. 4

BMW Parts:
Part #61.13.6.913.612 Four each.
Part 61.13.8.364.848 Four each

 

Stumbled on this post, trying to do the very same thing, have all the parts. Is it just a single wire from the control unit to the seat heaters. Or is there more to it?

 

It’s been a long time but I believe it’s a single wire. Certainly that’s what is prewired at factory and comes out under carpet along side of the seat rail.

Good luck 🍀



Back of control unit

 

Also I put this story on Rennlist (somewhere) and more details maybe added.

 

Thanks so much for taking the time to respond, I appreciate it's been years since you posted and did this.
there's a wiring diagram with relays and switches further down the thread that threw me.