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Discussion Starter #1
a few weeks ago kuhlmeister reported on his seat heater repair. I was about to replace my seat heater with an aftermarket pad set but decided to try the repair first.
I took pictures and have written it up as a pdf file. I do have more pictures if anyone is interested. It was time consuming but easy to do. I also stuck in some thoughts on how I would have added the aftermarket pads if I had gone that route.
I had to split the document into 2 parts because of all the pictures. the first 2 pictures in part 2 are the last 2 in part 1.
hope it helps someone.
cheers
Barri
 

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Looking at the burn marks on the felt, I'm surprised that nobody had a car fire yet. :eek:
 

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If all else fails, seat heater assemblies for the 202 series cars are available and can be trimmed slightly to replace at least the early 210 seat heaters. cost is about $120 per cushion or back. Also, at least on my seats, the two side bolster heaters are wired in series, the seat cushion heaters are wired in series and the combo is in parallel. In my case the seat cushion elements were broken. Now I have a backrest cushion element broken, I'll give this trick a try. Didn't look to hard when I replaced the bottom elements, thinking it would be difficult to find let alone repair. Looks like I was wrong, as long as there is only a few breaks.
 

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Discussion Starter #5
Thanks musikmann - but I bet you 50c you could do it :D
I was thinking the same thing Kobus - I know there were 3 po's before me and someone somewhere along the line had removed the fuses for the drivers side seat heater. I think probably when the seat back let out its smoke as that was a fairly heavy wire with lots of scorch marks :eek:
Thanks e420 I was thinking of it as I have seen you mention that in other posts but I got the carbon fibre seat pads from a truck equipment site - $39 for the set and all the wiring etc. Its going in my MG now:)
cheers
Barri
 

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DIY Retrofit Heated Seats in W210

I hesitate to start a new thread on heated seat retrofit because there are dozens of threads out there on this topic. Unfortunately, most of them are very short and light in details. As such, I am going to start a new thread while I do this project with the goal of consolidating as much information as I can into this thread.

This should be a fairly simple project but time intensive. The hardest part for most people will be running a retrofit wiring harness throughout your car. It goes to both front seats, both front and rear fuse panels, and a wire up to the center console where the seat switches will live.
 

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Obtaining Heated Seats or Retrofitting Existing Seats

WIS document AR91.30-P-0004A outlines process for retrofitting existing seats. Otherwise, seats obtained from other sources with the heating elements can be used. More than likely you will be installing this feature using seats that did not come with your car. I've read that the normal W210 parts require new upholstery if you try to retrofit existing seats as the heating elements are actually sewn into the covering. One post on the MBCA site said someone was able to use W202 or W203 seat pads to retrofit existing upholstery, however you'll have to do further research if that is a route you want to follow to make sure it is in fact a viable option.
 

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Retrofit Wiring Harness

The wiring harness I purchased for my 1997 E420 was part number 2105405208. According to the EPC, it is used for a large number of chassis codes though I can't say for sure if it is the same harness for both early W210's and later/facelift/2000+ W210's.

NOTE: THE WIRE IN THE PHOTO IS NOT LAID OUT IN A WAY THAT CORRESPONDS TO THE CAR! In this photo, the left side wires are for the passenger connection and extending back to the rear fuse box. The right side wire is the drivers seat connection and the ground wire branch. The thin wire coming towards the bottom of the photo will actually run under the drivers seat, up the side of the car and through the dash to the front fuse box. The wire in the middle towards the top of the photo is what will run to the switches in the dash.

The close up photo of two wires shows the connections that run to the fuse boxes. The red runs to the back, the back to the front.
 

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Installing the Wiring Harness

Attached is an overview document from WIS (AN91.30-P-0001A) that has a general diagram on how the wiring harness is routed through the car. The connections are listed as follows, however at this point I'm unsure if the codes provide specific connection points or if they are simply used for the diagrams.

F1-f12 Fuse and relay box F1
F4-f18 Rear fuse box F4
N25/5 Front heated seats control unit
N25/5s1 Left front heated seat switch
N25/5s2 Right front heated seat switch
X55/3 Left front connector block
X55/4 Right front connector block
W18 Ground (left front seat crossmember)

Based on the above, it appears that the section of the wiring harness with the grounds attached (brown wires) runs to the left seat. The other seat connection therefore is the right side, and it also has the thicker red wire with blue/green markings for a fuse box connection. So the thicker red wire must run to the back fuse box, down the raceway along the side of the car (which makes sense as it would be good to have a thicker wire running more directly to the battery for heating current). That leaves the thin black with white marking fuse box wire to run up to the front fuse box. Based on diagrams in attached file, this thin wire is routed via the left side raceway. And of course, the connection to the seat switches in the dash run up the transmission tunnel and behind the radio.

The 0001-01A document attached (thanks to Raymond- for this) further confirms that the thick red wire goes to the back fuse box.

Further, it says that color markings on the retrofit harness (stickers/tape) should match the exits from the cable ducts.... "The color coding on the wiring harness must match that on the main wiring harness. It identifies the emergence of the wiring harness from the cable ducts."

Unfortuantely, the markings are not extremely specific as far as I can tell -- both left/right seat extensions have green about a foot from the end, and then blue at the end. So it does not seem they are distinguished as left/right. So I am relying upon the instructions that say the left has the ground connection on the same branch.

Front seats and center console will need to be removed from the car to access the wiring raceways. You should be able to access the wiring raceways down the sides of the car without completely removing the carpets, though you will need to remove a few trim bits to access the edge of the carpets. Attached is a photo from Raymond-G's retrofit of heated multi-contour seats with his seats removed.

If you are installing seats that also have the multicontour option, you'll want to route the vacuum/air tubes at the same time according to instructions in other threads and/or the mercedes WIS.
 

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Connecting Wiring Harness to Front Fuse Box

See WIS document AN91.30-P-0001-01A (attached to previous post in english and a german version of the document is attached to this post).

You'll be fishing the thin back wire with white stripe up the side wire channel on the car and up behind the driver's footwell area. If you lower the panel covering the area under the instrument cluster and steering wheel and look up, you'll see a hole through to the engine compartment and fuse box. It would probably help to also open the hood and open up the fuse box (unscrew the larger lid, don't just open the flip cover). That will give you some light coming down through the hole to see where you are going.

For this connection, the WIS document says "1-pin connector (0.5 mm2, black/ white) to fuse box F1 fuse F1-12C."

The above text refers to the fuse area marked 12 and on the reverse there are letters with different slots for wire connections and the wire goes into slot C. Unfortunately, I wasn't able to immediately figure out what rows on the back corresponded to the numbers on the front. I should have counted the rows to see if there were the same number as listed on the front but didn't think about that before putting it back together (and not sure if that would have helped sort out which row to use anyway). I ended up leaving the wire fished up into that area for a later connection. I'll update this post with more info on how to determine the numbered rows from the back once I hook everything up.

Jim Condax on another forum advises, "When inserting the wires into the bottom of the connector blocks in the fuse boxes, slide the red locking bar about 1/8 inch to the right which will allow you to insert the connectors."
 

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Connecting Wiring Harness to Rear Fuse Box

WIS AN91.30-P-0001-01A document says "Connect 1-pin connector (2.5 mm2, red/green-gray) to fuse box in rear (F4) fuse F4-18D"

Also, this thread has a number of posts with info about the rear fuse block:
http://www.benzworld.org/forums/w210-e-class/1390310-diagram-fuse-box-under-rear-seat.html

As stated in the last step, Jim Condax on another forum advises "When inserting the wires into the bottom of the connector blocks in the fuse boxes, slide the red locking bar about 1/8 inch to the right which will allow you to insert the connectors."
 

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Wiring Seat Switches in Dash Console

The part number for the dash seat switches is A2108200151 (updated from A2108200051). This part number appears to cover most if not all W210 models, but always double check the EPC or with your dealer to be sure. This part is also used on W208/CLK cars. This has both left/right seat heater switches in a housing putting them at the normal far outside position in the dash. This part interlocks with the hazard/headrest/window lock switches that are the default for W210's.

You'll also need a new dash radio/switch bezel with the appropriate number of switch mounting holes for your set of options **OR** the WIS document says that you can "mill out" the switch positions you need in your existing panel. If buying new, I've read that you can also get one with ALL the switch positions open and then buy "filler" switch blanks to close up the ones you don't use. Of course, you could always just install the full row of switches and be content with some of them not working.
 

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Additional Information

Placeholder post for additional information such as the attached wiring schematic previously posted by raymond-g
 

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a few weeks ago kuhlmeister reported on his seat heater repair. I was about to replace my seat heater with an aftermarket pad set but decided to try the repair first.
I took pictures and have written it up as a pdf file. I do have more pictures if anyone is interested. It was time consuming but easy to do. I also stuck in some thoughts on how I would have added the aftermarket pads if I had gone that route.
I had to split the document into 2 parts because of all the pictures. the first 2 pictures in part 2 are the last 2 in part 1.
hope it helps someone.
cheers
Barri
thanks for the guide! I´m going to do the same thing on my car :)
 

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Base Only

If you only need to repair the seat base, and not the backrest, is there a way to do it without all the removal and disassembly?
 

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If you only need to repair the seat base, and not the backrest, is there a way to do it without all the removal and disassembly?
I think you must remove the seat in that way too...it´s easier to fix when you have the seat out of your car.
 

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Discussion Starter #18 (Edited)
yes - pasi84 is right (good luck with the repair) you have to remove the backrest to get the bottom cushion out. the backrest is only held on with 4 bolts but 2 are on the inside next to the console so you have to take the seat out. to be honest it only takes about 20 minutes (or less) to remove the seat and another 10 minutes to disassemble covers and remove the seat back. you dont even need to remove the wires to the seat back just pull it off and lay it next to the base.

It may be possible to get the skin undone from the base without removing the seat and seat back but I certainly would not try it for the extra time to remove everything
good luck with the repair Dave and thanks for posting kuhlmeisters original thread - I wouldn't have tried if I hadn't read that first
cheers
Barri
 

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Looking at the burn marks on the felt, I'm surprised that nobody had a car fire yet. :eek:
Not to dig up an ancient thread but I just purchased an '04 E500 wagon and the drivers seat bolster has a 1/2" hole burned through the leather. I though the lady burned in with a cigarette until one day I had the heater on and saw a column of smoke coming out of the hole. I found a broken and frayed wire shorting out and burning the foam and leather....:eek:

Thanks for the write up. I'm going to pull the seat apart and fix the heater before I have the leather repaired. I figured I couldn't be the only person to have this problem. I'm surprised their aren't more issues.
 
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