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Subject: Heated Front Seat Install - complete (MANY pics) Author: Rhett : member since March, 2005 : 1455 posts Posted on: 2005-12-20 19:47:16

This is my very comprehensive write up on how to install a heated seat kit into a 2000 740iL. The one I purchased, “Heizgerat Setzt II Seat Heaters”, came from www.autowarm.com (eBay for $163 for both seats). I will tell about my opinions at the end of the write up, but for now – here is almost every step of the way with plenty of details.

I warn you, this is long with many pics, but hopefully you can do this yourself after reading thru. One thing to note about the sensor in the passenger seat: I am pretty sure this only measures the weight of the passenger to vary the airbag strength. 99% sure that overlaying the heating element as I did will have no affect on it – factory heated seats still have that sensor, so we should be safe.

Enjoy

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Tools I used:
Torx bits – T-50, T-30 (3/8” drive)
3/8” ratchet for Torx bits
Universal driver (screwdriver handle type) with T-30 bit
Flat head screw drivers – large and small
Good pair of side cutters
Needle Nose Pliers
Pair of Channel Locks (for bending tabs)
Lots of 4” tie straps – buy good ones, not the cheapest
Razor Blades and/or Scissors
Hammer (for bending tabs back into place)
(4) wire taps

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This is for the front passenger seat.

Step 1)
Put the seat all the way back and all the way up


Step 2)
Remove (2) front Torx bolts with T-50 bit – don’t worry about the plastic covers yet.



Step 3)
Put the seat forward until you uncover the rear plastic covers on the rail.
Pry up very gently where screwdriver is shown (circled), and then put fingers where the 2 arrows are shown and pull up & towards outside of seat (think rotating up and away).



Step 4)
Remove Seat belt bolt with T-50 and remove clamp (circled) – I pried with a screwdriver till it popped out, but here is some pics on how that clamp works. Pull Seat belt up and out of the side panel and let hang free.






Step 5)
Lean seat back to an approximately 30-45 degree angle. Make sure headrest is down to about an inch of gap between it and seat. If you have the comfort seats, make sure to lean the shoulder forward some (5-10 degrees is fine).
UNHOOK the battery at this stage
***note – the entire seat will tip back as shown in the pic – let it rest on the backseat.



Step 6)
Unhook the connector for the seat. Insert screwdriver as shown and pry away from the connector and then pull the rest of the way.




Step 7)
Grab the seat and take it out thru the front door. I did this myself (I am 6’3, 27 years old and in good shape) the seat is awkward, somewhat heavy so if you need a hand..... get one. This is what you will be looking at now.
Put the seat somewhere you can work on it for 2-4 hours. I used the summer picnic table that was in the garage. You will be flipping the seat over a few times and working on both sides so it made it pretty convenient to be able to walk around it.



Step 8)
Put the seat on its side – switches facing up.
Remove (3) push clips holding the switch panel on. Remove (2) Torx screws from the panel (T-30).






Step 9)
Remove and unplug switches – good opportunity here to replace the old panels (which I did), so here is how to remove switches from panel too.

Pry to the left and this connector will separate:


To remove switch, push metal tab in on one side while pressing down, then push in other metal tab and switch will pop out on the painted side.


Next one was a little trickier. There are (4) tabs that need to be compressed while your pushing against the switch itself. After that, it will rest between the 1st and 2nd ridges and slide out. I used a straight scribe to push them in, I think now a butter knife would work great.



The big rectangular switch is easy, pry on (2) of the (4) tabs and it will pop out. To get the wiring away from the switch, pinch as shown and pull away from the box itself.


Then pry with a large screwdriver to unlock the clip the rest of the way. Note the grooves




Step 10)
At this point, I turned the seat over so the seating surfaces were facing down so I could remove the back covers (less handling this way). I am still not 100% sure on the easy way to get these covers off, but you can see (1 of 2) bottom clips in the next pic. You’re supposed to be able to stick a screwdriver in, press the loose end of the clip and pull all at once. I stuck a large screwdriver in there and twisted it. This was the most difficult part of the whole job for me…….



To remove the top cover, pull up where shown:



After that, pull the whole panel up at a 45 degree angle towards the rails. Grab the “loose” portion with your other hand and pull as shown.
****This is where the comfort seat needs to have the shoulders leaned forward a bit, you can see in the last pic that my bottom cover was still on and what angle the shoulders where to the main part of the seat….. I had no clearance to remove it so I had to take the top off first.


Closeup of clips on top cover:


Top cover removed:


After you get the top removed, and you have the bottom covers clips loose, the bottom cover will slide towards the top of the seat and come off.





Step 11)
Remove the seat belt latch (t-50) and unplug (2) connectors. Don’t unscrew the bolt all the way; there is a locking washer between the latch plate and the seat frame that will stay with the bolt – less chance of dropping it and having to chase it.


Insert small screwdriver into slot and pry as shown: Other connector is simple – pull apart.



Step 12)
Remove remaining side panel – (2) push clips and (2) t-30 torx screws (I had to use a nut driver with a torx bit on this one, my ratchet bits wouldn’t fit into the side panel deep enough)




Step 13)
Remove headrest. Push in the (4) little black tabs while pulling slightly on headrest. After all (4) are loose, grab seat with one hand and pull headrest out.





Now here where the fun begins…….


Step 14)
For the back cushion:
Pry up all the little tabs holding the leather in place. Use large screwdriver to get under them and then lift up. Try and get them to about a 45 degree angle up and it save you a step later by making it easier to get the leather back on. You can use the Channel Locks here too for bending up the tabs. Cut the wire tie holding the wiring/tube in place. Unclip where noted.



I just found out today (day after I did the install), that you can remove the green plugs and then separate the 2 halves of the seat. I don’t think it would matter too much for this.

For the seat cushion:
Pry up all of the little tabs here.




Step 15)
Remove bottom seat cushion and leather. Work the wires thru the leather and let hang.
Start from the front and pull up.


NOTE: PASSENGER SEAT ONLY has an occupant detection pad. You need to unplug it and cut the wire tie holding the harness to the spring.






Step 16)
Unwrap the remaining leather from the back of the seat. Start from the top corners. Mine was just a bit tight, but after you get the corners started it is a lot easier.



Step 17) (still on the seat back)
Clip all the hog rings – look for the green tube looking things in the pic, 1 or 2 rings for each one. There is (1) ring on each side that’s kind of buried towards the bottom of the cushion.







Step 18)
Remove all remaining bits of the hog rings. Needle nose pliers are a must at this point – small magnet would help too (or magnetized pliers). Grab the piece and twist out.



Don’t forget the pieces that are left in the fabric.


Here is the cushion with NO hog rings left



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

From here on is how I installed my particular kit. Yours might be different, or I might not have done it the professional way – but this was my first shot at them.


Step 19)
Lay top element (2 wire pad in my case) and mark location. You can tell just how much of my seat will be heated now. You also need to mark and cut the location of the (3) areas that had hog rings going across the seat. Trim excess width away. I used the edge of the adhesive (orange area) as a guide, just happened to be the perfect width.





Step 20)
Instead of Hog Rings – I used zip ties, they are WAY faster and easier – at least for me they were. In all of the green sections of foam, where the old rings went thru, there are holes now. It just so happens that the small 4” ties fit right thru. You need to use needle nose pliers here to fish them thru. Grab the tie with about 1/8”-3/16” of the tie sticking out, and insert into the hole. Make sure the angle of the tie going into the hole is in the general direction of the out hole. It will make more sense after you try a couple.

**NOTE direction of zip tie – very important for later. Also, to save time, have the locking part of the zip tie rest at the height of the foam (easier in next step).






If you don’t get it to come out the hole, it might be trying to go into the seat foam itself, a 90 degree scribe/pick can fish it out for you.


Finish product with tools used:




Step 21)
Peel off adhesive backing and place pad in location:



Cut supplied Teflon tape into 2” squares and cut an –X- into them, not a +. You will see why when you try and fold the tape over the cut edges on the heating element.





Step 22)
Route wires out the bottom thru the leather flap – next to the wiring harness and tube you saw in step 14.



Step 23)
Starting from the bottom of the cushion, put the wire tie thru old hog ring holes in the (2) pieces of fabric. Make sure the tie will clamp the metal rod within these fabrics. Don’t tighten the zip tie yet, do it just enough so it will hold for the time being. Do the 2 side first, then the (3) spots going across.








Step 24)
After all zip ties are loosely fastened, grab the end with your pliers and pull, placing your finger against lock area while pulling will amaze you at how easy it is. Hopefully you put the zip ties in the right direction and height. After all are tight, clip ends very short.
FYI – when you pull them tight, this is what gives the seat its recessed seam look.




Re-wrap the leather for the top half of the seat, don’t worry about attaching it yet, you will after you finish the bottom cushion.


Now onto the bottom seat cushion itself – this is very similar to the back….


Step 25)
Clip all hog rings to separate leather from the foam. Remove all bits & pieces of the hog rings.




What you see now is the occupant sensor (passenger seat only).



Step 26)
Layout and cut the (3) holes again, trim the edges to the right width and set heating element aside. Notice how long the heating element is compared to the cushion – that’s butt and thigh heat, lol. Don’t forget to mark on the end of the cushion where the element will stop.



Step 27)
Install the zip ties like you did with the seat back. One thing to note hear, 1 of the hog rings had gone thru the top of the green tube and didn’t actually grasp anything. Make your own hole – I used my 90degree scribe.




Step 28)
Peel adhesive backing off the heating element and put into position. Cut the insulating tape into squares with an X in them, and put over the holes (like previously done)


Step 29)
Re-attach fabric to seat cushion like in step 23. Do the sides and the cross part, save the last 2 on each side as shown for the final ones to do (easier this way).



Step 30)
Re-install cushion onto frame. Note that the lip of the foam goes over the lip of the seat frame. Route wires as you see fit – you won’t feel them so I just went straight out the back.




Step 31)
Sit back and look at your seat with the loose leather, not too hard huh.



Step 32)
Flip seat over so seating surface is facing down, you need to reattach the leather now using the tabs on the seat frame. Go back and double check that the tabs are bent upwards. If you grab the side bolsters of the cushion, that will help with stretching the leather into place.



Don’t forget this little strap





Step 33)
Zip-tie wires/tube together and reinsert into metal clip



Step 34)
Re-insert headrest. Get it started thru both tubes and onto plastic carrier. Grab both sides of the seat and push with your leg/knee until you here the tabs “click” into place.



Step 35)
Reinstall your back covers. I had to do mine in the car due to the angle of the shoulders, but this is the easiest time to do them.



Step 35)
Admire your completed seat, with tight leather.


And for direct comparison to loose leather.



Step 36)
Modify the side panel for the switch. If you have a uni-bit drill (recommended) you can just drill to the appropriate size, since I didn’t, I used this combination to get me close and then finished grinding to the right size. Make sure you put the large rectangular control boxes back in before you drill and double check clearances for the new switch







Step 37)
Install your old switches into new panel. Make sure you put the lumbar adjustment switch in right side up – it doesn’t quite fit the other way…..






Step 38)
Connect the wiring to the switches. Align tabs if needed. Route new heated seat wires thru hole as shown.




Step 39)
Reinstall Side panels. Don’t forget the push pin locations. You might have to fight the leather a little more to get to them now.





Step 40)
Reinstall seat belt latch and connect wiring.




Step 41)
Zip tie all the wiring together, zip tie to underside of seat spring out of the way and hook everything up except for the power and ground.





Step 42)
Remove clamp if you haven’t already from the braided line in the floor. Good time to vacuum/shampoo carpet and look for unwelcome guests.



Step 43)
Reinstall seat into the car. (4) Torx bolts, (1) seat belt bolt, the clamp, and connect wiring.


Slide seatbelt down thru here




Reinstall plastic covers:



That is all there is to it. From here, the only thing left to do is hook up to power source. What I did for now, was tap into the main wiring harness under each seat (car side). There is a large Brown (ground) and another large wire in each harness (positive). I used those, but the kit I bought will only be on if someone is sitting in the seat. So I don’t have to worry too much about killing the battery if I left them on (already left them on overnight yesterday, car started fine @ 10 degrees F).

Now for my opinions on the kit that I bought.
1) instructions say it takes 5-10 minutes for heat – this sucks, I want heat quickly
2) Doesn’t work unless someone is sitting in the seat – good because I can forget about them being on, bad because they don’t heat up when I let the car warm up in the morning.
3) Not quite as hot as I would like, it seems like they are getting warmer with use, but the temp rating is not as high as I would like.

Would I do it again – Heck yeah.

After – can’t even tell other than the new switch:


Total time:
5-1/2 hours on Saturday to do my driver seat
3-1/2 hours on Sunday to do my passenger seat, wire both, and take 170 pictures (yeah, I know I need help, lol)


2000 740iL - 149k miles & counting, 2 10" JL audio DVC subs and big RockFord Fosgate amp :)
5% tint back 3 windows, 30% on front doors,
Custom Straight-Thru stock mufflers with tips
Fresh tranny rebuild @ 145k miles thanks to Kirt

• Heated Front Seat Install - complete (MANY pics) (pic) - Rhett 2005-12-20 19:47:16 (12386 views)
  • Here are some general comments for everyone...... - Rhett 2005-12-21 20:31:25 (542 views)
  • Excellent write up! How about an 'active seat' retrofit? (nt) - s62fan 2005-12-21 18:18:17 (358 views)
  • Awesome post. David, youre gonna need a new raid array to hold Rhetts posts! (nt) - 740sporter 2005-12-21 13:28:11 (262 views)
  • You are the Magellan of these cars!!! - shaunhaywood 2005-12-21 11:44:09 (295 views)
  • Guess you're not interested in my how-to-change-your-own-oil post... (nt) - Peter 2005-12-21 10:37:26 (316 views)
  • Wow Rhett, Now you see why I put you in with the masters - bghark 2005-12-21 09:25:46 (237 views)
  • Wow, I'm truly impressed. Rhett how are you going to top this one? (nt) - kingdom7 2005-12-21 01:21:45 (266 views)
    • Well Done Rhett!!!! Geat Job!!!!Here are some pics from my new leather install. (pic) - HighLine740iL 2005-12-21 08:44:41 (574 views)
    • Thats easy - I found a source the other day (possibly) for massage & heat - Rhett 2005-12-21 08:13:49 (335 views)
  • It was like watching a movie a frame at a time. LOL - farnarkler 2005-12-21 01:12:38 (223 views)
  • Trivia question- how may write up derived from this job? 8-)) (nt) - bmw635 2005-12-21 01:09:30 (237 views)
  • WOW, you really wanted heated seats.....which I can understand! - Magnum 2005-12-21 00:00:54 (241 views)
  • let's not forget other DIY info one can garner from this post.... - Q 2005-12-20 23:41:37 (291 views)
  • Outstanding work. (nt) - davidc 2005-12-20 23:37:12 (195 views)
  • I've been entirely humbled. Un-f'in-be-leave-able. (nt) - ArbysNight 2005-12-20 23:29:34 (228 views)
  • I admire your ambition - BJames38 2005-12-20 22:13:35 (247 views)
  • Man, that makes my dash removal/ blower motor replacement - thesteve 2005-12-20 22:02:10 (398 views)
  • Nice details. Where is the slider clips mentioned in another thread? (nt) - collison944 2005-12-20 22:00:12 (248 views)
  • WOW! Great job! It's so complete it even needs a dial-up warning! (nt) - dwightf 2005-12-20 21:46:11 (230 views)
  • Re: Heated Front Seat Install - complete - ga7 2005-12-20 21:38:40 (336 views)
  • Job Well Done! (nt) - al1 2005-12-20 21:27:35 (265 views)
  • That has to be without a doubt the most photos I've seen in a single post LOL (nt) - tdaniely 2005-12-20 21:23:04 (206 views)
  • WOW, ambitious project, and excellent write up & documentation! - destined for E38.org! 8-) (NT) Q 2005-12-20 20:35:03 (243 views)