Active Comfort Seat retrofit (long!) to the Contour Seat...

Subject: Active Comfort Seat retrofit (long!) to the Contour Seat...
Author: ripp222 : member since January, 2006 : 389 posts
Posted on: 2008-09-01 12:32:13

I recently retrofitted the Active Seat (option SA455) to my driver's E38 Contour Seat and wanted to share my findings.

But first, What is Active Seat? Here's BMW's description from WDS:
=============================
Active Seat
The active seat features two liquid-filled plastic sachets (fluid bubbles) that are incorporated under the seat cushion. The bubbles are alternately filled and emptied thus gently moving the spinal column of the person sitting in the seat in order to relieve tension, stiffness, fatigue and backache.

Components
The entire active seat system consists of the following components

Buttons for driver's and front passenger's seat in the center console switch center with integrated function LEDs
Control units in driver's and front passenger's seats for controlling pump unit
Two liquid-filled sachets in seat cushion of each seat
Pump units in driver's and front passenger's seat

Function
Operating principle: Two liquid-filled plastic sachets (fluid bubbles) are integrated in the seat upholstery. These bubbles are uniformly filled when at rest. When the active seat is switched on, a pump is activated that empties one bubble and completely fills the other so that the seat surface is raised on one side. This status is maintained for approx. 10 seconds. The bubble is then emptied to the mid-position. After a renewed pause of approx. 10 seconds the bubble is completely emptied and the other bubble completely filled.

This process ensures that the pelvis is continuously tipped slightly resulting in movement of the lower spinal column. The muscles work permanently (as when walking) and do not suffer from fatigue. The body remains relaxed.

When at rest, both fluid bubbles are approx. 15 mm high. When the system is active, the height changes between 0 and 30 mm. Although the bubbles are incorporated under the seat upholstery no elevation in the seat surface can be noticed when the seat is not subject to load. The active seat can be activated as from ignition lock position 1 (terminal R). After switching off, the pump continued to run until both bubbles are in the mid-position.

Push buttons
The push buttons for operating the active seats are integrated in the center console switch center. The line to the control unit for the active seat is switched to low (ground) for 30 ms by pressing the corresponding push button in the switch center of the center console. The control unit activates the active seat and also switches the line to low (ground) for 30 ms. The function LED in the push button is then switched on. Feedback does not take place and the function LED remains off if the line to the control unit for the active seat has a break or if there is a fault in the active seat. No feedback is sent by the control unit when the active seat is switched off.

Pump unit
The pump unit contains the following components:

Fluid pump with DC motor: Pump with alternating direction of rotation for filling and emptying the fluid bubbles
Position transmitter (Hall-effect sensor): The mid-position of the fluid bubbles is recognized by way of the position values.
Pressure switch: The pressure switch (one per bubble) switches off the pump when the pump begins to build up vacuum. The bubble is then completely empty.
Solenoid valve: The solenoid valve prevents the fluid flowing back

Fluid bubbles
The fluid bubbles are filled with a water-glysantin mixture. They are connected to the pump unit by means of plastic hoses. The pump unit and fluid bubbles must be replaced together in case of repairs.

Control units
Control units that control the pump unit are provided for the driver's and front passenger's seat. The control units are connected to the P-bus. The corresponding coding as to whether the control unit operates the driver's seat or the front passenger's seat takes place via Pin 5 (signal name COD) at the 6-pin plug connector of the control unit. The pin in the control unit on the front passenger's side is connected via a line to vehicle ground

The control unit for the driver's seat contains an acceleration sensor that registers the transverse acceleration of the vehicle. Operation of the active seat is temporarily interrupted at very high transverse acceleration levels.
=============================

BMW only offered this option on their Comfort Seats, so I expected a few issues along the way. I found two...

1) The bottom seat cushion for the Comfort seat w/ Active Seat is unique. When the cushion is molded using Polyurethane Rubber a set of hard boards is laid on the bottom of the mold. As a result there is a hard surface for the fluid bladders to push against during operation. You can pull the boards off the Comfort seat cushion and use foam adhesive to attach them to the Contour seat cushions, though this will increase the cushion height by 1/4 inch or so. The Active Seat operation WITH the boards moves more of each side up and down, which I could see being necessary if your bottom was "wide". Without the boards the operation was a bit more subtle, more focused towards the center of the seat. As such I didn't deem it worth the time to glue them in. In addition, I wasn't sure if the leather cover would be as tight with a raised center?

2) The seat springs of the Contour seat frame don't line up with the clips on the black plastic trays under the liquid bladders. As such the clips needed to be ground off or partially removed in order for some of them to line up with the springs. To compensate for some of the clips no longer being present, I drilled 2 small holes in each black tray and ran a single zip tie to help keep the trays from sliding off the springs. I believe they are supposed to be anchored at the rear, then as the spring stretches (you sit down), the pad can slide on the springs at the front.

Parts Needed for BOTH front seats:
52 10 8 234 873 ACTIVE SEAT DRIVE (x2 @ $1130 each)
52 10 8 248 217 SET PAD (x2 @ $6 each)
52 10 8 234 874 ACTIVE SEAT DRIVE BRACKET (x2 @ $11 each)
61 35 6 901 558 ACTIVE SEAT VENTILIATION CONTROL UNIT (x2 @ $239 each)
52 10 8 234 867 FOAM PAD, ACTIVE SEAT w/ LEATHER (didn't use in my installation)
61 12 6 908 571 WIRING DRIVERS SIDE @ $155
61 12 6 908 587 WIRING CO-DRIVERS SIDE @ $133
61 31 6 927 072 CENTER CONSOLE SWITCH UNIT @ $282
Electrical Contacts (x2 for the main seat harness connector and x2 for the central switching center)
20 gauge wire, 5 feet per seat

These are only needed if you replace your seat foam:
52 10 1 945 543 CLAMP [aka Hog Ring] (x25 @ $0.09 each)
88 88 6 520 050 PLIERS @ $46

Note: you don't need BMW's hog ring pliers, I purchased C.S. Osborne pliers from Rochford Supply and they worked fine.
While I was ordering I also picked up a can of their adhesive spray and leather pliers for pulling the leather off the seat frame, as I was replacing my seat foam due to normal wear on the side bolster.

As you can see from the pricing, this would be an expensive retrofit with new parts being almost $3400!! Fortunately people part out 2001 750iL's (Active Comfort seat was standard) and occasionally the leather is damaged, leaving only the seat parts to be sold. This is how I obtained my parts (thank's Scubba Steve!).

You could skip the wire harnesses and just make your own as there is only one 6 PIN connector with 4 wires needed for the driver's CONTROL UNIT (Power, Ground, P-Bus and Center Console Switch signal) and 5 wires for the passenger CONTROL UNIT. The below instructions assume you've done this.

1. Lower headrest, move backrest upright, move thigh rest in (Sport Seats)
2. Remove single T50 Torx bolt from seat belt anchor on lower seat frame
3. Disconnect seat belt height cable from rear of seat bottom and remove 2 rear T55 Torx bolts from seat rails
4. Remove 2 front T55 Torx bolts from seat rails
5. Lower window and place towel over door panel, also place towel over rocker panel (don't want these getting damaged)
6. Disconnect main seat wire harness
7. Remove seat
8. Remove rocker panel trim and lower B-pillar trim

9. Lift up carpet and unravel tape from both ends of abrasion sleeve on existing seat harness
10. Thread single wire through abrasion sleeve and into PIN 16 (assuming elecrical contact is attached)

11. Run this single wire along navigation / radio harness up to center console (I looked at running the wire along the main harness towards the front of the car, but then you have to go behind the instrument cluster and HVAC box in order to get to the center console)

12. Remove Nav / Radio, then HVAC control, then Central Switching Center
13. Run single wire into PIN 22 (assuming electrical contact is attached)

14. Re-wrap wire harnesses and secure single wire with zip ties
15. Remove 2 T20 Torx bolts from front of seat rail and tilt back (you will want to disconnect the harness from the seat travel motor and seat belt receptacle side trim in order to gain more angle between the seat rails and seat bottom)

16. Cut plastic ties in order to free up existing seat harness
17. Unravel tape from existing seat harness and feed single wire into main connector PIN 16

18. Locate power (Red w/ Brown stripe), ground (Brown) and P-Bus (Red w/ Blue stripe) and solder 3 wires accordingly

19. Re-Wrap seat wire harness and zip tie
20. Feed fluid bladders through center of seat rails (note: if you have the 4-way lumber you will need to remove the air pump assembly, remove the black plastic bracket and then install the air pump into the Active Seat bracket on the next step)

21. Install Drive Bracket onto seat frame

22. Plug 6 PIN wire harnesses into Control Unit and clip onto Drive Bracket

23. Slide black tray and bladder above seat spring

24. Align rear corner 2 clips to seat and then cut black tray as need to allow it to lay flat on seat springs

25. Mark 2 holes, drill 2 holes and feed zip tie through to secure black tray

26. Rotate seat back onto seat rails and install 2 T20 Torx screws
27. Place seat back into vehicle, install 4 rail bolts, seat belt anchor and seat belt height cable

28. Turn key to position 1 and test Active Comfort Seat

Enjoy the ultimate seat!
Now if we could just add Active Ventilation (the perforated leather w/ 8 fans) and still keep the seat heaters! Can't have it all…

My ride...

04/1999 build 740i, Anthracite w/ Black Montana Leather
MODS...
0-006-783 Clear Indicator Set w/ 6-904-837 & 838 Clear Tail Lights
9-115-032 MKIV Computer w/ 6-923-879 Widescreen Monitor
1-422-379 Vavona Wood / Leather Shift Lever
2-265-542 Wood & Chrome black headliner handles
6-964-398 New Gen BM53 Radio and 6-906-082 Antenna Amp
0-303-079 OEM reversing camera w/ 0-303-083 Video switchbox
Rear Seat Sunblind Control
Automatic Rear Headrests
Active Seats
Passenger Seat Memory

The 7 Series E38 Forum | Message Thread:

Active Comfort Seat retrofit (long!) to the Contour Seat... (pic) - ripp222 2008-09-01 12:32:13 (11416 views)
- excellent job! I always wanted active seats. Where did you get the switch unit? (nt) - ian 2008-09-01 19:59:40 (247 views)
  - Scubba Steve (ebay) had the complete 'kit' from a car he was parting. - ripp222 2008-09-01 21:38:01 (248 views)
    - For reference, after studying the parts to retrofit the passenger seat... - ripp222 2008-09-05 11:15:05 (220 views)
- Pure genius!!!!!!!!!!!! Very impressive write up.!!!!...Now if someone can - snitch740i 2008-09-01 14:10:48 (217 views)
- Awesome write up. - 740ilDuke 2008-09-01 14:00:57 (183 views)
- Please post a picture of the pliers. Thanks. (nt) - J A M E S. 2008-09-01 13:36:08 (187 views)
  - Photo of pliers (special tooling)... (pic) - ripp222 2008-09-01 21:44:53 (387 views)
    - Thank you sir. I'm wanting to fix a loose leather seat surface... (nt) - J A M E S. 2008-09-01 23:20:32 (186 views)
- I'd love to do that retrofit. Great work! (nt) - DavidC 2008-09-01 13:18:51 (195 views)
  - Minor typo, perhaps the moderator could fix? - ripp222 2008-09-01 21:50:42 (191 views)
- Awsome job man! nice MOD! glad I have them stock save me a lot of work :-) (nt) - Edwin 2008-09-01 13:18:22 (203 views)
- Nice work, Jay. Looks awesome. (nt) - Ed 2008-09-01 13:05:12 (181 views)
- Tremendous retrofit and excellent documentation. (nt) - J A M E S. 2008-09-01 12:51:43 (183 views)
- My most wanted upgrade...I envy your seats. (nt) - Stygian7 2008-09-01 12:39:14 (224 views)

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