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Thread: Rear Heated Seat DIY Writeup Install

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    Rear Heated Seat DIY Writeup Install

    There doesn't seem to be much on this topic via search and the only "write-up" I found here>>> http://bimmerboard.com/forums/posts/1066203 simply covers the basics. I have a 04/2001 build date and my friend who also has a late 2000 build '01 model ALSO was missing the necessary body harness needed to do this conversion so it debunks the idea that late models should already have this wiring. In this writeup, I'm going to cover everything you need to do to get the seats working. I'm not going to cover however, the pictures and removal of the center console and fishing the wire under the carpet.

    As covered by the link above, this is the seat harness you need to provide power to the heated seats and also provide illumination to the center switches.



    If your passenger wiring looks like this, you'll need the body harness section necessary in completing the conversion.



    This clip is the body harness section that you will need. You will only need 3 wires from this harness, 2 of which will need to be traced back to the source. The brown which is the ground wire going to the passenger side C-pillar ground block, and the green/white, which runs back to fuse 63 (terminal 30) covered in pictures below. The purple/lavender wire with red stripe is the illumination which actually runs all the way under the front passenger seat to a terminal block. It will NOT be necessary to pull the wire from the source. I suggest just getting a foot or two to splice locally. (Also covered below) If you're curious, the red wire is used for the rear seat adjustment and I'm only guessing the last multi colored/stripe wire is associated with that.



    As you see, the seat harness only uses 3 wires.



    Since I have no intention of installing the rear adjustment and also don't want to run the extra 2 wires, I chose to de-pin the 2 unused wires. You can choose to cut them if you're feeling lazy.



    Feed your green/white and brown wire through with the rest of the harness wires and secure them. The brown will go to the C-pillar ground block while the green/white will continue through into the trunk.




    Along the same bundle where the body harness clip will be mounted, find the lavender/red illumination wire and splice your lavender/red into that by whatever means you like. Do NOT cut the wire as it's clearly going to something else but splicing into it won't be an issue.



    Feed the green/white wire through and secure it along the other wires.



    Take notice of the dark green relay and the space to the right of it. We will be installing a second one which is part of the factory wiring.




    Now that you've gotten the "easy" stuff out of the way, this is where things get a bit more complicated and in all honesty, had I known I would have had to do all this, I probably would have just said eff it, I don't need the rear heated seats for those that never ride in my car anyways. Originally, I had just spliced in green/white wire that you just ran above into the fuse slot. I kept popping the 5A fuse 19(F19) at the main fuse panel but only in certain conditions. This is what caused to question the wiring further and go back to my friends parts car for more research.

    This is the other dark green relay and associated wiring you'll need to pull. Thankfully, it's all in the trunk and easy to trace back albeit dealing with the sticky black tape. The wires you need to trace back are the green (which goes to the rear fuse panel itself and supplies the necessary power to fuses 62-68), the Red wire which goes back to F104 next to the battery, the smaller green/blue wire which goes back to the rear fuse panel and will be our trigger ignition wire so the seats can't be left on when the car is off, and the brown wire which goes back to the tail light ground block next to the battery.



    Now, where were we....
    Once you have your rear fuse panel free, start off by undoing both clips on either side to release the black wiring assembly from the holder.




    Once you have it free, you'll need to slide this holder out almost all the way. You can take it out completely if you'd like. This is a SECONDARY means of holding all the wires in place and is necessary to complete the rest of the processes. Do NOT worry, your wires won't just fall out as it takes much more work to remove them.



    Remember the green/white wire you ran from behind from the body harness, under the rear parcel and into the trunk? This is where you can terminate it and clip it in place. Slot number 30 or better known as Fuse 63(F63). (I apologize ahead of time for not covering the de-pinning process at the fuse panels but if you have a small flat blade similar to the size used for watches and sunglasses, or purchase a small pick set from harbor freight or where ever, you'll need the small straight one to de-pin. Depinning is always done from the front side of the block where your fuse is inserted, not the back side as one would think.)



    Once you have the green/white wire snapped in place, you'll now need to de-pin the green/blue wire just behind it. The below picture is the solid green that you'll need to de-pin from your parts car that tied into the dark green relay and will replace the green/blue in YOUR car. The green blue is what is fed from F19 up front. At first, I thought this would be an absolute pain to de-pin BUT, I found out that if you gently pull on the wire while sticking in your pick or small flat head screwdriver, that it will release the clips. Take note by the picture that there is ONLY 4 you have to undo. 2 in the front, and 2 in the rear, the middles don't have anything. These clips face the front of the car and the picture is taken in the same manner it would go into the fuse panel.



    After you install along the back side of your fuse panel, DON'T FORGET to re-insert the white slide lock assembly you pulled out earlier. Your fuse panel should now look like this. Take note of the factory green/blue that you just depinned and is now dangling behind the thick red. This will be used later in this writeup.



    Let's take a little break and go over the actual wiring diagram so you can start to understand better what we're trying to accomplish and the why. Your ignition switch supplies power to F17-F24.


    F19(5A) is the green/blue wire toward the right and runs alllllll the way back to the rear fuse panel and provides switched power for fuses 62-68. Fuse 62 is for your auto dimming mirrors and is also a 5A fuse. If you had done like me where you just plugged in F63(15A), you would be blowing F19. This is why we NEED to install the secondary relay so the power being drawn is from the rear power block next to the battery F104.




    K93 is our new dark green relay that I mentioned above. Now when you turn on your ignition, The green/blue from F19 will supply power to the K93 relay. The brown wire which we will cover below is the ground that runs to the ground block by the tail light. The solid green that you just clipped into the rear fuse block above is the new power source for F62-F68. The red wire which we have yet to cover will run back to F104 next to the battery.




    Okay... back to wiring.
    From the new relay, run your red wire back to the distribution block next to the battery and terminate here.



    Run the thin brown ground wire next to the tail light and land it on any available slot.
    (By now you should know how to remove the black cover housing)



    Secure all your wiring and it should start to look like this.



    Now, the ONE thing we have left to cover that I'm sorry I don't have a picture for is what to do with the green/blue wires... If you remember, you de-pinned the factory thicker Green/Blue out of the rear fuse panel that ran from F19 and left it hanging. You should also have a THIN green/blue that comes off of the relay you just installed. What you'll need to do is (GULP) CUT your factory F19 somewhere close to the 7 prongs and splice that into the thin green/blue for the relay. This will complete all the paths of wiring needed to get the seats working.

    Reassemble everything and your setup should now look like this.




    This covers everything needed to properly install the rear heated seats into the factory wiring harness as if it came from the factory. Although I didn't cover this in the writeup, I'm confident based on taking apart one of my seat cushions partially, that you CAN cut the factory hog rings that secure the leather, foam and heated seat element off of a seat that doesn't match your interior color, and with a bit more work, transfer the pad to yours. It is not "sewn" into the leather as some believe. Once of these days, I may do that to my bottom cushion since the one I have is a non-sport (no piping along the edge) but the ones I installed are of similar quality that I just may avoid the hassle all together.
    Last edited by PiotrC70; 10-29-2017 at 04:18 PM.

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