I have read the archives regarding heated seat retrofitting as I would
like to add this option. When I look under the front of either front seat there are 3 separate wiring harness couplers, two of which are connected.

Am I wrong in assuming the third is for the heated seat option? I suppose it could also be for the lumbar bladders... or both...

I looked at the parts diagram and it shows heating elements only for the seat bottoms. Is it true that the seat backs are not heated?
One poster indicated that the backrests are heated but could be wrong...

Thanks

Good question. The heating is so weak on mine that I can barely tell it is working. I am thinking about putting some new elements in. That is interesting that you mention the heat only being in the bottom because that is all I can feel. I really want the heat in the back to help with lower back pain on long trips. I hope someone can shed some light on this.

thanks for the imput, I had an E430 and the seat heaters were fast and hot

Parts diagram does not show an element for the backrest

Would you mind looking under your seat to see if all three harness' are plugged in?

Well, I thought I was doing you a favor and you ended up doing me a favor. I went out to my car (in the rain) to look and see what connectors are connected under my seat. When I looked under there I saw that all three were connected. I started digging a little deeper and found that the one going to seat heating element only looked like it was plugged in an actually was not connected at all. I plugged in in firmly and lo and behold, it heated right up. And yes, the bottom and back both heat up.

ok, that is good to know, was it the center connecter that was unplugged?
that is the one on my car that is not connected...

I read in the archives that all W208 CLK come prewired for heated seats
so retrofitting is relatively easy, just new bezel with buttons fishing out harness behind bezel plugging it in. Same under seat...

Hardest part seems to be taking the seats out, removing the leather covers and fitting the elements....

Thanks for checking and good to know yours are now working!

Yes, it was the center one that was unplugged. It is the one with the heaviest gauge wires.