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How to: OEM Front heated seat retrofit

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Hi folks. I completed this retrofit a few weeks ago, but went straight offshore afterwards. Now here's the write-up. This will give you OEM spec front seat heating with switching and functionality as BMW intended. Non-OEM generic heated seat kits are available on Ebay, etc, but I didn't fancy that myself. Parts of this guide may still be useful if you're fitting aftermarket kit.

BMW Parts Required:

Heat Element Mats - OEM BMW heated seat mats are available on German Ebay from seller bmwe46driver. As of 08/2012 he has listings here...

Non-Sport Seats

Sport Seats

Of course these links will not work in the future, but just go to Ebay.de and type something like 'BMW NEU Sitzheizung' and you should find them. You can ask the seller in your best German ('Guten tag, do you speak english?...) to make sure they come with the right plugs for your model/year. These elements can be installed in your existing seats to make them heated seats. Or...

Already Heated Seats - Alternatively, get yourself some second hand already heated seats to save yourself some work. I went with the mats as my existing seats are excellent condition leccy comforts, so I wanted to keep them. A note on used heated seats: Make sure they are really heated and work! Some seats (mine included, and I'm guessing maybe all electric seats?) have part of the heating loom installed even if they are not heated. So the pins for the heating elements are actually populated in the main seat connector, possibly fooling you into thinking they are heated seats when they are not. To be certain, measure resistance/continuity between the heated seat power pin and the main seat earth pin. According to BMW info approximately 10A flows during heating @ 13.8V, so expect to read about 1.4 Ohms. If you read double, one of the two elements (base or back) could be broken. If you read open circuit you either have no heat elements, or they are broken.

Heated Seat Retrofit Loom - BMW part no. 52 11 0002132 gives you a complete plug-and-play wiring loom for about £60. Alternatively you can DIY using the wiring diagrams as a reference, although it will be a pain without the metal contact parts with which you populate empty connector pins and fuse receptacles, etc, unless you can salvage these from a scrapper. BMW loom well worth it, imho.

UPDATE: For those who fancy DIYing the loom, Chi has done this and made a great guide here...


Buttons - You'll need to replace your whole Switch Centre (the row of switches under the climate control panel) with one that includes heated seat buttons (and your existing buttons). Easy enough to find if you have a common set of existing buttons like just PDC and ASC/DSC, but if you have a more exotic list of existing buttons, e.g. blind, sport, etc, it can be harder to find your replacement. I got mine (heated seats, PDC, DSC and blind) from German Ebay. Type something like 'E39 Schaltzentrum' (German for Switch Centre) or list some of the buttons, e.g. 'E39 PDC DSC Sitzheizung (seat heating)', and you'll find them.

Other Parts/Info:

Hog Rings and Pliers - If you're doing the full mats install into existing seats, the leather covers are held on with metal hog rings. You need new ones and special pliers to put it back together. Or...

Cable Ties - The far easier (cheating) modern alternative to hog rings that saved me endless swearing (more later) :)

Various Tools - Socket set (including Torx), screwdrivers, side cutters, etc.

Sliding Jaws - Does your seat clunk when cornering? Mine did so I used this seats-out opportunity to apply the BMW official fix. See my thread for more details...


Official BMW Heated Seat Retrofit PDF - Not hugely detailed but useful to have around for reference. Two versions depending on model year. Check the E39 sticky thread for links.

Wiring Diagrams - Bring up and print the correct wiring diagrams for your model/year from the link in the E39 sticky thread for reference.

Here's some of the bits ready to go. Switch Centre and loom...


Heated seat mats...



This stage is all you need to do if you just want to wire in some existing heated seats you have obtained. Pretty straight forwards and not very time consuming if you have the BMW Retrofit Loom.

NOTE: My car is a 2001 with some changes in wiring and the newer style seat connector compared with older models. If in doubt refer to the correct BMW Heated Seat Retrofit PDF and official wiring diagrams linked above for reference. If you have the earliest E39 that has individual buttons rather than the all-in-one Switch Centre and would have had the old style potentiometer-dial heated seat switches, then the wiring is quite different and this guide wont be correct at all. You can still do the job but follow the correct wiring diagrams religiously. I believe it's actually simpler in a way than the later cars with only power through Fuse 32 and ground to be supplied to the heat switches, then from the switches out to the seats.

First take the seats out. Run them fully back to access the front bolts


Then fully forward to access the rear bolts. Unclip the plastic trims


Disconnect the seatbelt and the wire for adjusting the seatbelt height


I then ran the seats to the middle which means the runners dont stick out the front or back making it easier to take the seats out of the car without risking scratching your paint/door cards. Also adjust the seat height fully upwards giving you more room underneath between the seat base and the runners to work on later. When the bolts are out and seat in correct position you are good to unplug the main seat connector underneath the front of the seat.

NOTE: If you turn on the ignition with a seat disconnected you will trigger the airbag warning light. So unless you have the cable/software to reset the light, dont turn on your ignition until you are finished and the seat is back in.

With the seats out, you can pull that little cable a few times and watch the seatbelt height move up and down and think 'wow what cool engineering'. Then start dismantling the dash area to fit the wiring loom. Carpet strips off - undo screw then they slide forward to unhook


Take the panel under the glove box out and, in the drivers side, the panel under the steering column out (disconnecting the interior speaker as you go). Next the front door shut trim panels need to come off. They have three plastic clips as shown below. You need to prise them off with a screwdriver right by the clips and they'll pop off quite easily. Prise away from the clips and you'll crack/deform the panel first.


Then the vertical door shut/footwell outer panels can come off. Passenger side just popped off easily, drivers side needs you to remove the bonnet release lever first. The plastic clip required quite a pull, so it helps to know where it is to pull in the right place (the top)


In the centre console take out the cup holder (two screws)


Then reach in and pop out the old Switch Centre and the Climate Control panel.


I later took the whole frame out for better access - may as well do this now. Just some more screws


You're now ready to start fishing the wiring loom through.

NOTE: The BMW Retrofit Loom is in two parts - one is wiring from the Switch Centre out to the seats, and the other part is for power and K-bus from the car, via Fuses 45 and 32 to the Switch Centre. If you have the factory rear blind or active seats (yeah right) then you already have this second power loom installed. The BMW Retrofit PDF doesn't mention this second loom at all (!) and as I didn't need to install it since I have the rear blind, I can't give detailed instructions with pictures. But here's how I think it goes...

Installing Power Loom (if Required):

You'll need to take out the glove box to get better access to the fuse block. The power loom consists of 4 wires:

Red - this goes from the main power connector under the carpet on the driver's side floor...


...connection point X3, Fuse F111 (according to the wiring diagrams) to the supply side of Fuse 32.

Red w/ blue stripe - this goes from the load side of Fuse 32 to the Switch Centre pin 7.

Violet w/ blue stripe - from load side of Fuse 45 (supply side already populated) to the Switch Centre pin 23.

White w/ red stripe/yellow dots - K-bus from K-bus connector behind the glove box somewhere (look for other wires the same colour) to the Switch Centre pin 21.

Installing Main Heated Seat Loom:

The passenger side leg (white w/ green stripe and white w/brown stripe - but check diagrams for your car) is easiest to thread through to the back of the dash as you can just about see all the way through to where it needs to be. Thread it through to the right of the metal bar all the way to the back where you can retrieve it the other side and pull it all the way through


The driver side leg (white w/ yellow stripe and white w/ blue stripe) is harder to thread through as there seems to be nowhere for it to go! I eventually got it through going to the side immediately behind the metal bar and was able to retrieve on the other side behind the lower dash trim panel and pull all the way through


You can then plug the four pins into the Switch Centre main connector (slide off the black outer cover first) according to the wiring diagrams - passenger side wires into pins 1 and 12, and driver side wires into pins 13 and 22 (check diagrams!)

Back to the passenger side leg, I routed it with the bundle of wires running over the top of the glove box out to the side of the car


Then down behind the sound deadening (there's a convenient cut in it) and carpet towards the floor


Then run it in the plastic cable conduit towards the B-pillar. Remove the piece of green foam for access


The brown earth wire exits first and plugs into a spare slot on the fan connector


NOTE: If you are installing used factory heated seats you may notice the heated seat ground pin in the main seat connector is not populated (only power and sensor). That is because when assembled in the factory the seat heat element ground wires are connected through (a solder point) to the common seat ground pin. Therefore if you are installing used factory heated seats you dont actually need to install these brown ground wires. If you are installing mats into existing heated seats, you install these ground wires as the heat mats will use this alternative route to ground (and the plug will be so populated) rather than having you unwrap and solder into the main seat ground.

The other wires continue on and can be run with the existing seat wires all the way out to the seat connector and plugged in (referring to the diagrams)


Tie them to the other wires for tidiness


NOTE: You'll find there is excessive length on this passenger side leg. I tied the excess up above the glove box.

Over to the driver side leg. From where you retrieve it behind the dash, I routed it up along the existing wiring over the top of the steering column


Then down behind the sound deadening and carpet and along the cable conduit as per the other side


Now something funny happens here. You'll see the existing seat wiring emerges from near the centre of the car (near the transmission tunnel) rather than near the outside of the car like on the passenger side. The brown ground wire of the OEM BMW Loom actually isn't long enough to reach from the seat plug to the ground point if you follow this route! Therefore you have to make the retrofit loom emerge from the carpet on the outside of the car as it does on the passenger side and can't run it along with the existing seat wiring. A new slot has to be cut in the carpet for this, mirroring the other side


Plug the wires in (referring to the diagrams).


With the carpet back in place you can see exactly what I mean about the retrofit loom having to take a different route or the brown ground wire is not long enough to reach the ground point


You can now reassemble the interior. Before you reassemble the dash, you can at this point test your work to check everything is good. You can either plug in your heat element mats before installing them into the seats or plug in your used heated seats to test them


NOTE: As I said earlier - do not turn your ignition on to do this test without full seats plugged in unless you have the kit to reset your airbag warning light which will come on without the seats plugged in (well technically it's just the seatbelt pre-tensioners that are required)!

If all is good, and you are installing used heated seats, you are now done. Reassemble everything and enjoy your toasty roasted cow (or cloth if you're poor :)). If you are installing heat element mats in your existing seats read on.

Installing Heated Seat Element Mats in your Existing Seats:

This caused a bit of frustration! If you look at the Ebay ad for the OEM heated seat mats you can see a picture of suggested installation where the mats are placed directly onto the seat foam with the leather covers presumably refitted over the top. This is the method I tried first, did the whole passenger seat and reinstalled it into the car for testing. Dissappointed is an understatement! Dont get me wrong - it wasn't a total disaster - a comforting mild warmth eventually permeated through from the seat (or was it just my body heat?), but I was expecting serious toastiness, especially on the 3-LED max setting.

Thoughts like 'are these not actually OEM spec heaters' or 'is my Switch Centre faulty' etc went through my head. It just wouldn't do. I had a hunch as to what was going on, so I had the seat out again and stripped down to investigate. Sure enough the reason was clear. The leather covers include approximately half a sheep of fibre wadding stitched into them. Although this is presumably for comfort, it also acts as excellent thermal insulation (think of your loft). So it's no wonder that having all that insulation between your heat element and you means you dont feel much toastiness at all! In the factory, these heat mats would have been an integral part of the leather cover, sandwiched in directly against the leather with the wadding and other layers the other side. To get the heating to function properly the mats would have to be installed in that way. That meant taking scissors to the covers! :)

If this scares you (it really shouldn't though - it all worked out in the end :)) you could always take the easier first method, and as I said you will feel some warmth if you concentrate, but I highly recommend you do it 'properly'. It's a bit harder and a bit more work, and somewhat irreversible after you've used the scissors in anger, but well worth it in the end! :)

So with the seats already taken out of the car we start to take them to bits. Undo the plastic trims on either side of the base. They each have a couple of Torx screws and some plastic clips. One screw position near to the seat back hinge is buried by the seat cover so you need to push it out of the way. Alternatively, you might find it's already broken like one of mine so doesn't need to be removed :).


If you can get some needle-nose pliers behind the clips and squeeze them in it helps them to pop out. Some you cant access behind so carefully prise them off and if you're lucky you can do it without damaging the clips. This shows what I mean when I say you can squeeze from behind to help them release


On electric seats you need to release the switch wiring. Each switch has a different method of releasing the plug - like it was a little design competition for some work experience students :)


I'm not exactly sure what occurs here with manual seats, but I assume you can detach the levers somehow. You also need to undo the seatbelt pre-tensioner wire and feed it back through the leather in order for it to come off. Note the little elastic band that holds the wire up and remember it later


On the passenger seat, remove the first aid kit bracket. On the driver's seat remove the fire extinguisher bracket if fitted. Now onto the seat back panel. I have read some of these have screws in the bottom. Mine do not - they have metal clips that can be a pain to release. If you try to pull them off, you will most likely experience the sound of your back panel creaking ready to rip/break. You can help matters by inserting a screwdriver or dinner knife into the side of the seat to push the metal spring clip in to help it release. This is what you're trying to do


And the clip released. As you can see you kind of really wanted to push the other side in to release, but good luck with that, and at least this helped :)


The seat back panel then slides upwards to unhook at the top. If you have Comfort Seats the back panel is in two parts so you need to remove the upper part in the same way, although the bottom clips are rotated 90 degrees


You need the headrests off. Not sure about manual ones, but electric ones are held in with ball and socket joints, so a sharp pull upwards pops them out and you can release the headrest


You're now ready to detach the leather covers. They are stretched on over metal hooks in the frame which you just unhook. You might need to bend them out occasionally to make that possible



Go all the way round the seat bases and backs unhooking the cover. If you have Comfort Seats note the arrangement of this piece of elastic which holds the leather in place at the backrest top hinge so you can put it back correctly later


The bottom flap of the seat back cover has two sets of holes you can use. Note which holes are used for correct reassembly later. Mine use the top set of holes. I have a hunch that cars with lumbar support would use the top set of holes to give the seat cover some slack for the lumbar support adjustment, whereas cars without lumbar support may use the bottom set of holes to pull the cover nice and tight. But I'm not really sure!


Be sure to note how on the corners near the seat backrest main hinge the cover is folded and a few flaps share the same hook. With the covers released you can remove the seat base cushions completely from the frame. Sports seats will no doubt involve some additional fiddling due to the extending thigh supports


NOTE: Disconnect the passenger side occupancy sensor wire before removing that seat cushion.

To remove the seat back section you need to disconnect the back frame from the base frame at the hinge. Remove the green lock clips


Then push down on both latch release levers (two screwdrivers are good) and pull up on the seat back frame to disengage from the base


Pull yourself some slack in the seat back wiring loom and lumbar support air hose if present (cut some cable ties if necessary), then you can place the seat back frame on the floor. Now you can remove the seat back cushions


To remove the leather covers from the foam cushions you need to remove the metal hog rings


I just used two pairs of long nose pliers to open them out then remove them. With the hog rings removed you can remove the covers from the foam


You can invert the sides and fold them round the back to get them out of your way


There's a thin layer of fabric, then under that, this is what I mean about the padding/insulation. It's pretty thick and not surprising the heat elements dont work through it very well at all!



It took me a while messing about under that annoying top layer of fabric until I realised that because it's only connected round the edge, I can turn the cover inside-out to get it out of the way. Ta da - gone, and not cut off in frustration as it nearly was :)


The wadding must now be removed, so get busy with some big kitchen scissors and a craft knife. Cut as close to the stitching as possible but dont cut the stitching or your seats will slowly fall apart


It comes off in three pieces on the back and five pieces on the base


I dont want to loose any of the standard comfort, so these pieces of padding are reinstated on the foam. Back




Some double-sided tape helps hold it in place for reinstallation of the covers, but once the leather is back on, hog ringed in and tight, it wont be going anywhere. Back to the covers, with the wadding gone you can now position the heat mats over the leather. Be sure to pinch plenty of slack material over the metal wires and the central stitching lines. Again some strips of double sided tape can help keep things in place and avoid creases later

UPDATE: After some time I would say it's pretty important to get the heat mat well stuck nice and flat to the leather. I tried without tape on my second seat and the heat mat has creased underneath the leather in one place due to movement. Better than double sided tape would be some spray contact adhesive. When you are happy with the position of your heat mat, stick it in place so it will not move and crease later. You could also stick the pieces of cut padding onto the foam.


Now here's what I think is the clever part. Hog rings are all well and good, and the special pliers close them down very nicely, but the difficulty is access and making sure you're hog ringing all the right layers of stuff together in all the right places. Easier said than done. So I decided cable ties were the way forward. The length and flexibility mean you can install them in the cover first, then later when you refit the covers to the cushions you can install them all at once nice and long so that everything is in place before you tighten them up. They'll be more than strong enough (dont use the really piddly small ones - mine are 140mm x 3.2mm). After coming up with this myself (honestly) I did some googling and found, unsurprisingly, that plenty of DIYers and pro-upholsterers alike have already thought of this :).

So with the heat mat positioned you can pierce holes in the mat and insert the cable ties through the mat, through the original hog ring hole in the seat cover (be sure you go behind the metal wire) and back through the mat.


Note the direction and orientation of the cable ties, chosen so that when you put it all back together you can grab the pointy end, thread it through the hole at the back and zip it up



Cable ties installed in base


With all the ties in place you can invert the covers to get the layer of fabric and the sides back where they should be. Make sure you pull the cable ties through the holes in the fabric layer


During this inverting you'll disturb your mat, even if held with some tape, so make sure it is spread nice and flat over the leather so you dont have creases underneath the leather after installation. When you're ready to install, position the cover on the cushion. The heat element wires need to go through the foam to the other side so that they dont have to be wrapped around the metal seat frame. Make holes with a knife and feed the cables through. Base


And where it emerges the other side


This is where the cable emerges on the seat back


Begin to thread the cable ties through the original hog ring holes in the seat foam. I used a knife to pierce slightly larger holes and used long nose pliers to help pull the cable ties through. Fix the cable ties with just a single click of their ratchet for now so you have as much clearance and adjustment as possible till the final tightening



When you're happy everything is in place and there are no creases in your heat element mat, you can tighten down all the cable ties


Then trim off the tails

Pull the covers over the sides of the cushions and reposition the cushions on the seat frames. Be sure the heat mat wires are not pinched in. Now start to stretch the leather back over the hooks making sure the covers are first pulled tightly over the side bolsters. Bend any hooks back that you had to bend out previously to release the covers. Use the correct set of holes when stretching the bottom flap of the seat back cover back onto the hooks. Route the backrest heater mat cable down with the existing wiring/lumbar support air hose


When the backrest cover is in place you can reattach the backrest frame to the base frame. Just fit it back over the arms and push it down till both latches lock in place, then reinsert the green lock clips.

Plug the backrest heater mat plug into the socket on the base mat wiring then clip the wires safely to the frame springs


Route the main plug down towards the main seat connector. The main connector slides backwards off its mounting bracket after you release some plastic latches underneath for easier access. Slide the back black plastic cover off the connector which allows you to take out the existing heated seat plug section (if present at all from the unused factory loom I mentioned earlier) and insert the plug from your new heater mats


Then fit the back cover back on and fit the main connector back on its bracket.


Now fully reassemble the seats fitting the switches, brackets, trims, back panels and headrests. Remember the occupancy sensor plug on the passenger seat and the seatbelt pre-tensioners. Install the seats back in the car, reconnect the seatbelts and seatbelt height adjustment wire and plug in the main connector.

Now switch on your ignition and go for a drive with your properly toasty heated seats. It works exactly as it should do with the mats directly up against the leather. Despite all the hacking about that had to be done there is no loss of comfort or the shape/form/tightness of the seat. If you got this far, congratulations!

Edited by Liam79

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Um, dunno :). I dont really mind. I've just noticed the editor autosaves so I'm not worried about losing it all, so I'll probably just finish it all off in the next edit.

Edited by Liam79

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Thanks Ray! Totally worth it, especially here in Norway, and not too long a job. Wiring was done over a very lazy weekend. I had the passenger seat out for a week or so working on it slowly and thinking about it. But after I installed it that first time and it worked like crap, I had it out, completely stripped, done again properly and back in all in one evening. Drivers seat was done the next evening.

Now for the rears! :) You must have taken a few rear benches apart in your time - what actually holds the leather covers on those? Presumably not the same stretched over hooks arrangement as there's no metal frame? Or is there?

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Amazing write up.

Very informative and clear. Thank you for taking the time to do it.

Can we sticky these write up's Rob? There was a good rear leccy blind one a while ago plus there are Ray's threads as well...

Edited by Piper

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Thanks Piper! Rob gets round to adding these to the sticky thread if you PM him. He's added a few recently, but I'm sure, as you say, there is loads more good stuff that could be added. It does say right at the top of the thread 'If there is something you think should be in here, please PM me.'. My previous car (Vauxhall Omega) had a great forum with loads of really good DIY picture guides from the users, from mundane maintenance tasks to major work, and it was a real asset to the community. I'm sure buried in old threads we probably have the same here - it's just a matter of collecting it and adding to the sticky :).

Once I've decided how anally OEM I'm going to be with the wiring I'll be cracking on with my rear seats, and will do a write-up for that too.

Paddy - good luck!

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Now complete. Enjoy. And I want at least one other nutter to attempt the whole job :)

I want to do this now! Sitting here showing your thread to the other half she thinks I'm mad!! Truly superb write up ... Well done indeed.

We should look at trying to make them into PDFs!

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I'll be (considering) doing this too. Superb write up mate. I've got electric column, memory mirrors, auto lights and must finally finish my OEM Bluetooth retrofits to do first though....

Not enough hours in the day!

I'll sticky this at some point soon, again, no time!

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Thanks for the compliments, guys. Good luck Rob, when you get round to it. If anyone doing it wants to ask anything, just drop me a PM.

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I'm afraid Rob is right. It gave me all the handy metal bits for populating empty fuse locations, etc for fitting my boot socket. The whole loom kit was about £60 inc VAT from BMMiniparts.

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Ha ha sorry. If you do it yourself you'll end up paying a good chunk of that buying the individual metal bits seperately to make all the connections, plus wire etc. Alternatively if you can cut some connectors and bits out of a breaker you could do it that way. Depends how much you like work and hassle. Me, a few years ago I'd have done the same. These days I am prepared to pay a bit for an easy life :).

Edited by Liam79

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They have these metal spring clips that don't seem to pull off without inserting a knife/screwdriver to help release the clip. I describe it in the write up above. Might be easier to take off the bottom part first.

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Not sure what you mean. Unless you're having the same experience I did once (despite it being my own photo!) which is staring at it for ages wondering what the hell is going on. Then my brain image recognition skills stopped malfunctioning and I could see it is the end of some needle-nosed pliers being used to pull a tie wrap through a hog-ring hole in the seat foam. :)

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