Wiring Seat Heat Elements

The following VFAQ was created to help people install seat heating elements. As always remember the lovely legal disclaimer that I do not accept any liability for yours or anyone’s actions who may follow any of my guides.

Ok so you've already done the real work, installing the elements themselves under the seat covers, well now is the time to finish it off so you can finally start enjoying your investment. The wiring seems to go pretty straight forward, it is very helpful that Mercedes set the car up for this option in the fuse panel. I don't know about you but I despise seeing extra wires ran to my battery, it looks very low quality IMO. So what we are doing here is setting up the whole electric system for your new seat heaters.

I bought a kit which came with four seat heaters, four switches, one relay, and all the harnesses required to wire it up. It was quite a bargain and a very nice kit to work with, however I only desired to put the seat heaters in the front two seats because of this I only ran one circuit. Mercedes originally had their wiring setup such that the front heaters go on one fuse and the rear heaters go on yet another fuse. If you are indeed wiring up four seat heaters you may just as well do this. My harnesses were modified such that I only had the system left for the front two heaters, pretty much I cut off the rear harnesses including the power wire which ran for them inorder to make it easier to run the wire around.

Well a few things will have to be disassembled, if you are very patient fishing wires through it'll be next to nothing but since I don't mind pulling an extra part off here and there I just went ahead and did that. Quite often you can use a cheap steel wire to run through first and then tape whichever wire you want through and pull it through that way. I think it is pretty well mandatory to remove the ash tray, driver side kick panel, and center console. However the climate control is quite optional.
Ash Tray: Open it up all the way, see that tab in the middle? Push it down then roll the tray out the rest of the way. Now that it is out that is peachy keen but since we need the wood off the bracket that it attached to also has to come off. There are just two little bolts that hold that into place. After removing that remember to unplug the harness off the left side of it.
Center Console: With no bracket in the way anymore the only thing left holding it is the wiring which is connected to the switches and possibly a screw in the back of it. If you can easily see a screw in back you'll have to remove that, not all the years had this some had a system where if the wood slid back slightly it could come up. Well now that the wood is loose go ahead and carefully lift it up and unplug each switch one at a time, work any direction you feel like. I normally start with the closest to me and work away. If one is being real stubborn which they all could be if they haven't been touched in a while then I'd suggest pushing the tabs in at both ends of the switch and popping the switch out. Now that the switch is out and above the wood there is no fear of breaking something, grab the switch with one hand and the harness with the other, pull!

Kick Panel: As can be seen in the below picture there are several phillips head screws holding it in place, don't forget the one by the ebrake. Also be careful pulling it out, it is possible to break the hood release handle (guess how I know). Just in case you don't know you use a very small screwdriver to pop the plastic covers off the three screws on the top front. The side touching the console has to come inward otherwise it'll never come forward, the part is locked in back so the only thing it can do is come forward.

Now that that is out of the way let the wiring begin! I choose to have my switches in the center console so that is where the heart of the wiring will remain. Everything will branch off from there. I took the harnesses marked front left and pushed them down beside the console inside of it. Looking closely you'll see there is a gap on bottom, after all they did put the seat belt warning wire there as well. We are going to run the harnesses out around this area on both sides.

Ok now let's do the easiest wire, the ground. I went ahead and put it on the bolt next to the shifter, noncoincedentally where the ground of the light which lights the shifter is. This bolt is in the frame quite well so it should make a nice ground. Make sure that your wire clears all the supports and is below all of the things it should be. I wrapped mine around so that I didn't have to cut the wire off.

Well the only real work in this whole thing is the hot wire, it can't be avoided so I suppose now is the time to give it a whirl. Since I cut my main line into just two wires rather than four for four heaters I just electric taped up the length of those two wires then ran them through. The lines on the pictures are the path I took. If you fish a wire down from the top then you probably won't have to remove the climate control like I did.

Tools:
Phillips Screwdriver
Wire Stripper/Crimper

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