Power Lumbar Support Installation Tips
by Steve Cooperman 1/17/2000
We are reporting alternate installation techniques for the BMW power lumbar support accessory kit. Lumbar support has been available to European buyers but was not introduced to the United States market. The BMW part number is 52.10.9.404.379 and it fits E-36 models from 9/94 on.

This is a collaborative effort based on the installation experiences of members of Suzyıs M3 Digest who were participants in the first and second group purchases for this kit. In no particular order, the contributors are Jim El Nabli, Garrick Louie, Wayne Miller, Shawn Roberts, and Steve Cooperman.

Common sense should be used by the person installing this accessory kit since they are responsible for any unexpected results.

This information supplements the BMW instructions and includes tips that can simplify the installation process. It will make more sense after you have read the instructions.

The BMW instructions are printed in several languages. To simplify things you can photocopy the English instruction page, cut out the instruction sections and tape them over the German text. This is easier than flipping pages back and forth to compare written instructions to the illustrations.

To remove the headrests, sit in the seat backwards (facing the seatback). Push upwards while moving the headrest front to back. The front/back movement helps the bars slip out of the spring loaded stops. Sitting backwards allows you to brace the backrest with your knees or legs so the seatback doesn't get too traumatized. You may need to recline the seatback a little to get clearance from the roof as you remove the headrest.

Moving the seat forward and to its highest position gives greatest access for the installation. Remember to disconnect the battery cable before disconnecting any wires. If any sensors are disconnected while the power is on you may set a fault that requires a dealer to reset the airbag warning.

The seatback levers must be removed. These are the levers that release the seatback so it can fold forward. They pull straight out. Use a screwdriver to pry them out but donıt pry against the cover piece below the lever or it may break.

I used two small blocks of wood on both sides of the lever and two flat blade screwdrivers to pry out the lever from the seatback. Hold the lever halfway up and pry from the top and bottom using even pressure. The wood blocks are taller than the plastic piece so that they act as a fulcrum instead of the breakable plastic cover.

Another technique is to hold the lever halfway up and use a 3/8" wide slotted screwdriver to pry the lever straight out from behind using your hand as a fulcrum.

The covers under the seatback levers are removed next. Do not try to pry the covers out of the seat because they will break. The covers are retained by two clips on the top and bottom ends. These clips go into the seat and are held by barbed ends that clip around a piece of plastic. To remove them, place the tip of a flat blade screwdriver inside the opening and flat against the plastic clip and follow it to a plastic cross piece. Stop when you reach the cross piece. Push upward on the top piece and rotate the screwdriver outward to pull that end out. Repeat with the lower piece and push downward to release the barb and rotate outward. You only need to move the clip about 1 or 2 mm to release the retaining clip. It doesnıt take much pressure and you will not damage anything.

There are two screws at the bottom corners of the backrests that must be removed. They are Torx head screws (T-20 size). Using a Torx bit with a ratchet handle gives easy access to the screws.

The BMW instructions in the F 36 51 524 P illustration tell you to remove four clips. Apparently not all cars have these clips. If you canıt find them, donıt worry about it.

Remove the cover at the bottom/back of the seat to make the power plug easily accessible from the back. You need to remove this cover to route the wiring from the bottom to the lumbar support motor. The Torx screw that holds it in place is large (T-30). The other end of the cover plate is snapped in place and pulls off. Pull downward and it comes off.

Install the lumbar cushion as directed by the illustrated instruction. Do not attach the pump motor with the zip ties until the power cable has been routed from under the seat to the seatback.

The BMW instructions instruct you to insert the lumbar support cushion³ in the direction indicated by the arrow². The arrow is imaginary as far as I can tell. The lumbar cushion is placed in the seatback from the bottom of the spring toward the top.

Here is what I did. I pulled the lower spring (the one that extends across the backrest) back and inserted a 1.5 inch block of closed cell foam at the extreme side positions between the seat spring and the back of the cushion. This moved the spring back enough to be able to insert the lumbar cushion. The blocks need to be far enough to the side so that the lumbar cushion will fit between them. Wood or any other kind of spacer should be ok to push the spring away from the seat. Make the spacer as thick as needed but use the smallest thickness possible to avoid overextending the spring.

The next problem is that the seat cushion back is foam and is grippy. The lumbar cushion does not want to slide over it. I used a sheet of paper between seat cushion and the lumbar cushion to make it easier to slide the lumbar cushion in place. Don't forget to remove the paper after the lumbar cushion is installed.

It is difficult to feed the lumbar cushion into the space available between the seat cushion and the springs. I had to feed the cushion in at about a 90 degree angle to the seat back and then pull it through a fraction of an inch at a time. Your fingers will fit through the wire supports just enough to do this. You will be adjusting and feeding from the bottom, then pulling up from the top to keep things smooth. Finally it will be in place and you can hook the top tabs around the wire to keep it in place. The support wires are wrapped around themselves at the frame and have the ends sticking out. These ends can puncture or cut your hands so use caution in this area.

The BMW instructions direct you to remove the seat from the car and to remove the seat cushion for the lumbar installation. We have found that these steps are not necessary. The technique to avoid these steps is outlined below.

Remove the Torx screw (T-30) and unclip the plastic cover (as described above) from the very bottom of the back of the seat (the one that covers the motor). Move the lower part of the seat all the way forward and recline the back of the seat all the way down on the rear seat. Feed the socket to the pump motor through the hole in the lower seat frame that the heater wiring runs up. You'll need to pull the lower cushion toward the front of the car to reveal it. Run the socket along the path that the seat release cable travels and you've done the hard part.

It is easy to remove the cover plate for the actuator switch. The cover is retained by clips on the ends of the cover. Push the retainer clips toward the center of the plate with a screwdriver and it comes out very easily. Use an inspection mirror to help visualize the area.

All manipulations can be made from the side or back of the seat. Instead of laying upside down to view the underside of the seat, sit on the floor outside the car and use an inspection mirror.

If you need more access space, you can unbolt the seat (two bolts and two nuts) and just tilt the seat back to the rear. This really isnıt necessary, but you donıt have to lift the seat out unless you really want to.

The power supply connection can be confusing. The instructions describe power plug ³d² connecting to the plug housing for the electric seat adjustment. I interpreted (incorrectly) that it plugged into the seat adjustment switch. WRONG!!!

There are two power plugs (plug/socket) in the lumbar support wiring harness. You should remove the power supply plug coming from the floor to the seat. Connect the plug from the wiring harness to the (now empty) seat power socket. Snap the wiring harness socket housing to the plug that you just inserted into the seat (they have attachment points on the side of the plugs to do this). The power supply from the floor plugs into the socket from the wiring harness.

A different explanation of the power supply connector is that it is a Y-splitter (similar to a computer when you need to add a CD-ROM drive and add a Y-splitter to the power supply). This may help to visualize what is required for the power connection.

It is easier to route the wiring harness for the actuator switch through the hole in the seat and then connect the plug to the switch. Then simply push the switch into the mounting hole and snap into place.

There is a plastic cover piece attached to a power plug on the wiring harness. It is not needed when installing in a car with power seats.

Miscellaneous information:
Under tools and materials required, there is a universal knife mentioned. Nobody has figured out what is to be cut or why.

One thing that is confusing about the lumbar cushion itself is that they are the same for both sides, meaning the hose comes out on the right facing forward, although you would expect them to be "mirror-inverted." This puts the pump's wiring connector on the left side of both seats although on the passenger seat, the seat harness comes up on the right side. This turns out to be a non-issue as there is plenty of cable length.

I feel that the inspection mirror is the key to not removing the seats. Actually seeing how the parts fit together is necessary (for me anyway).