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Subject: Automatic Rear Electric Headrest Retrofit SA499 (long)... Author: ripp222 : member since January, 2006 : 124 posts Posted on: 2008-01-26 09:31:43

I finished retrofiting a portion of electric rear seats to my 740i and wanted to share my findings.

In the begining... a few observations after disassembling my rear seat:
- the left and right rear back rests have molded openings in the upper area of the foam for the headrest motor
- threaded bolt holes exist in between the headrest supports for the headrest motor
- a threaded stud is on the left side for holding the control module
- the seat cushion foam has molded openings in the corners for switches and a metal bracket
- ETK shows seperate part numbers for a bracket and switch cover to support a SINGLE switch in the rear seat corners (vs. the set of switches on a 750iL with full electric seats)

So it appears there was an option for automatic electric rear headrests in the short wheel base (series option SA499 according to www.7-forum.com). I even came across a photo off Ebay.de from a 750i



Time to retrofit!

Scuba Steve was kind enought to be parting a 750iL last year and I bought most of the parts I needed:
8-370-338 CURRENT SUPPLY HARNESS
8-370-798 WIRING ELECTRIC, SEAT ADJ REAR
8-166-671 HEADREST MOTOR, LEFT
8-166-672 HEADREST MOTOR, RIGHT
8-366-364 CONTROL UNIT HEADREST REAR
8-352-291 LUMBAR SWITCH, LEFT
8-360-877 LUMBAR SWITCH, RIGHT
8-352-289 HEADREST SWITCH (X2)
8-162-767 LOWER SEAT BELT RECEPTICLE (X2)

Hear are the new parts I bought for my black rear seats:
52-20-8-177-369 SWITCH COVER, BLACK, RIGHT
52-20-8-177-370 SWITCH COVER, BLACK, LEFT
52-20-8-186-669 METAL SUPPORT BRACKET, RIGHT
52-20-8-186-670 METAL SUPPORT BRACKET, LEFT
61-31-8-360-287 REAR LEFT HEATREST SWITCH BUTTON
61-31-8-360-288 REAR RIGHT HEADREST SWITCH BUTTON


The 750iL harness set is overkill as it supports the electric backrest and 4-way lumbar. I won't be installing the electric backrest as there are several brackets missing from the car frame that would need to be welded in place (and I can't find them in ETK).
I may install the lumbar at a later date, but the seat backs don't have the horizontal wires for supporting the inflatable pads, so it may be tricky. If you have no intensions of installing rear lumbar, then I'd say use the SWITCH COVER and METAL SUPPORT BRACKET for the short wheet base cars, just like in the above photo (there are different part numbers in ETK).

Here's an overview of new parts, with arrows, from top to bottom: Headrest Motor Assembly, Control Unit, Seat Belt Recepticle w/ Sensing
Switch. The circles represent connectors I'm NOT currently using, from left to right: Air Diverter ValVes, Backrest Articulation Motor, Air Pump.



Comments:
- swapping the 8 369 416 HARNESS (heated seats only) for the 8 370 338 HARNESS (fully electric w/ heated seats) was only difficult in
that you have to pull the old heated seat connectors between the carpet on the drive shaft tunnel area. I definitely recommend tying 2
pieces of string to each heated seat connector BEFORE you pull it though, so that you can pull the new harness back. I actually had the
entire center console out for a different reason, which gave much better access. If you don't have heated rear seat, then no worries.

- the electrical wires to supply the additional power were already on my vehicle main harness, behind the right seat back, so it was plug-n-play

- I couldn't find the part number for the headrest motor mounting bolts, so I used M6 x 10mm (four of 07-11-9-915-057)

- You may want to reinforce the threaded nylon piece at the bottom of the "cork screw" on the motor assemblies, one of mine split in two right at start up and I had to epoxy it back into postion

- the seat bench harness is more difficult for several reasons... You need to straighten out most of the metal tabs around the bench frame in order to partially remove the leather cover, exposing the seat foam. Then use a long blade to cut out the foam (there are 4 corner marks to guide you, but I say cut a bit inside of them). Then squeeze the metal support bracket into place and line up the bracket holes w/ the seat frame holes. I used 1/4 inch aluminum pop rivits to secure the bracket to the seat frame - it worked well! Then pull the leather cover back into place, secure by bending tabs back into position. Cut a small X into the seat leather where the foam opening is and start to pull the leather inside the opening. The metal brackets have their own tabs that the leather will have to be pierced by and then pulled over (I had to make small slits in the leather). Finish by bending the metal bracket tabs back into place.

- You will need a dozen zip ties to secure the wire harnesses to the seat bench

- I removed the metal clips on the headrest guides, they are no longer needed w/ the headrest motor assembly and they just make noise everytime the headrest is electrically raised.

Note: You could skip the whole seat bench harness install and cutting of the leather. You would have no switches, but still have automatic headrest movement when the seatbelt is fastened. This would save some money and save you the pain of cutting into your leather.

Here's some pics from the foam / leather cutting session...
















All done...



Happy Modding!



My ride...

04/1999 build 740i, Anthracite w/ Black Montana Leather

Updates...
8-150-492 Front Strip (liscense plate delete)
0-006-783 Clear Indicator Set
9-115-032 MKIV Computer w/ 6-923-879 Widescreen Monitor
1-422-379 Vavona Wood / Leather Shift Lever
New Gen Radio comming soon...

• Automatic Rear Electric Headrest Retrofit SA499 (long)... (pic) - ripp222 2008-01-26 09:31:43 (794 views)
  • I am blown away and thoroughly impressed! Dude you rock! - IBHenry 2008-01-26 21:41:37 (23 views)
  • Very, Very nice- like my sig says, its NOT what you buy, its what you build! - Mgood 2008-01-26 21:23:08 (18 views)
  • Terrific work! This will be on e38.org tonight! (nt) - davidc 2008-01-26 16:12:31 (24 views)
  • Sweeeeeet !! Well done ! (nt) - Krazy D 2008-01-26 15:38:23 (20 views)
  • wow! Very nicely done. This should be put on e38.org (nt) - ian 2008-01-26 14:30:02 (21 views)
  • Great job, looks OEM. (nt) - Buck 99 750iL 2008-01-26 14:25:09 (17 views)
  • well done, I am going to be doing this as well to my car to complete my 750 int. (nt) - 04sshd 2008-01-26 12:15:59 (22 views)
    • Forgot one photo... the scary one. (pic) - ripp222 2008-01-26 17:37:52 (99 views)
  • Very Nice!! So what about the adjustable seats? (nt) - visionbmw7 2008-01-26 11:42:45 (23 views)
  • Nice one! It's on my list............... (nt) - Edwin 2008-01-26 11:11:56 (28 views)
  • Very nice job with great write up :) (nt) - szos 2008-01-26 10:59:54 (24 views)
    • Re: Very nice job with great write up :) - audiavant 2008-01-26 12:38:17 (20 views)