BMW E36 Coupe
Power Window Motor / Regulator
The power window motor and regulator are essential to paying tolls, effectively
the IQ calculated for idiots who drive slowly in the left lane and, of course,
Several years ago one of my power window motors was operating intermittently. Research revealed that this symptom was typical of impending window motor failure, so I decided to replace it. That motor failed again a couple years later and that time it failed completely (i.e. the window was stuck fully up).
Normally, due to the manner in which the window motor attaches to the regulator (A.K.A. "Scissor Arms"), the regulator must be removed from the door to remove and replace the motor. The problem is this procedure requires the window be moved to a specific height to expose certain components as required to disconnect the regulator from the window itself, yet the window will not move if the motor has failed completely.
If your motor is intermittent but still operational, this will make life easier. If the motor has completely failed, it will be necessary to follow a slightly different optional procedure outlined below. Pay particular attention to the tools required for this task and make sure you have the tools required for the optional procedure if necessary.
Note that if your vehicle is equipped with side impact airbags, you must take extra steps as outlined or this task will result in illumination of the airbag warning annunicator in the gauge cluster. If this occurs, proper diagnostic equipment will be required to clear the fault.
- 10mm box end wrench
- 10mm hex socket and ratchet
- 5 mm allen socket and ratchet
- T20 Torx screwdriver. Do not substitute a socket...the outer diameter of the socket will be too big.
- [Optional] For inoperative motors only, a T30 bit and bit ratchet. Do not substitute a standard torx socket and ratchet...the assembly will be too deep.
- T30 socket and ratchet
- Spray-type lithium grease
- 5 Minute Epoxy (optional: needed only if door panel breaks)
- 2 hobby brushes suitable for use with epoxy and grease.
- 4 (¼ x ½) inch long cap head bolts, regular washers and nylon locking nuts.
- Dremel with cutting disks (recommended: use only “reinforced” disks for your own safety)
- Safety Glasses
Parts (Quantities are PER DOOR)
- (1) Window Motor
- (1) Regulator (optional, but recommended)
- (2) Sliders (get at least 3, preferably 4...they're cheap)
Removal / Disassembly Procedure
- Position the window fully up. If your motor is inoperative, continue anyway.
- Remove the door panel and disconnect the wiring for the speakers and side mirror.
- Disconnect and remove the airbag. Disconnect the yellow connector on the forward side of the airbag unit and then use a 10 mm socket to remove the four mounting screws. Set the airbag unit aside somewhere safe.
- Remove the foam insulation. The insulation is attached to the door frame with some black adhesive evil goo resembling uncured RTV. Try not to get any of it on you unless you like to spend 15+ minutes cleaning up.
- Mark the pivot adjustment current setting. Using a sharpie or other means, mark the door frame where the edges of the pivoting adjustment bar mate to it. The adjustment bar allows the window to pivot slightly in the door frame in order to fine tune its alignment with the door frame and retaining the current alignment should save a considerable amount of time and hassle.
- Try to "fix" the motor temporarily. If the window motor is inoperative and the glass is not in the fully-up position try to persuade the motor to come back to the land of the living. Try hitting the frame of the motor lightly half a dozen times with the handle of a screwdriver. I was able to bring my motor back from the dead using this technique. IMPORTANT: If you are unable to move your window to the fully-up position and out of harms way, be advised that using the wrong tools or techniques in the process required to remove the regulator rivets may result in the destruction of the window. You have been warned.
- Remove the regulator mounting rivets. Four rivets hold the regulator to the door frame. Don your safety glasses and use a nail set or drift punch of appropriate size (no bigger than 1/8”) to drive out the center of the rivet. Then use a Dremel with a reinforced cutting disk to cut an “X” pattern in the head of the rivet. If you intend to reuse the regulator, avoid digging into it. Use a small flat-blade screwdriver or chisel and a hammer to break each quadrant of the rivet head off before using an awl or the same small screwdriver (face must be 1/4” or less) to drive out the shank (back half) of the rivet. Oh, and by the way...unless you like the sound of metal rattling around in the bottom of your door as you maneuver your car be sure to remove the fragments from inside the door as you remove each rivet.
- Partially lower the window. With one hand pressing the mounting plate of the regulator to the door to keep it from moving under the considerable torque provided by the motor, with a few short taps of the window control carefully move the window down to a position where both ends of the regulator arms and the sliders are visible in the cutout in the door frame. This should result in about 4 inches of window exposed above the top of the door. Make sure you temporarily reconnect the airbag before you turn the ignition key to provide electrical power for this step or you will trigger an airbag warning. If the motor is inoperative, continue to the next step, otherwise skip it.
- [Optional] Remove the window motor from the regulator. To do this you'll need a low profile bit ratchet and a T30 bit. The tool must be low-profile because the screws that fasten the motor to the regulator are located on the rear of the regulator (facing the door) and the regulator assembly can only be pulled about 2" away from the door without bending it. Disconnect the electrical connectors from the window motor and, using the bit ratchet and T30 bit, remove the three motor mounting screws. Given the limited clearance this requires some patience, but it IS possible. Once the motor is free of the regulator it will be possible to move the window up and down by hand as outlined in the prior step.
- Remove the rear window stop. Although there are two window stops, we only need to remove the one located at the rear end of the rear window slide rail. The stop is fastened with two 10 mm bolts. One bolt goes through the window into a blind nut. The other is more or less a set screw that digs into the slide rail. The bolt that goes through the window must be completely removed, while the “set screw” need only be loosened 3-5 turns, or just enough to disengage the rail. Due to clearance issues, box end wrench is the best tool for this job. To pull the stop clear of the window and rail, pull it slightly toward the rear and then straight down.
- Unmount the pivoting adjustment bar from the door frame. The bar is secured to the door frame from the inside of the door with a 5 mm allen head bolt. In order to gain clearance to remove this bolt you may need to move the window up at least half-way.
- Disconnect wiring. Disconnect the airbag / door lock wiring loom from the top of the regulator and the electrical connectors from the window motor.
- Remove the regulator. This is the most difficult part of the entire process, IMHO (yes, even easier than the rivets) because it's not exactly intuitive. However, I can simplify the process by citing the general motion sequence required to extricate the regulator: back, forward, back. Pushing the regulator toward the rear of the door initially will push the rear slider beyond the point where the window stop used to be and out of the rail. From that point pushing the assembly forward sufficiently will allow the pivoting adjustment bar to clear the door frame opening, and pushing it rearward again will allow the forward slider to pull out of the forward slide rail. This process can require some aggressive tugging on the regulator and may actually break one or both slider clips but that's one of the reasons I purchased new parts. Once you have the regulator out of the door it's all down hill from here.
- Reclaim the motor mounting screws. Remove the old motor from the old regulator and set aside the three T30 Torx mounting screws. These screws do not come with either a new motor or a new regulator, so they must be reused. As you remove the motor, take note of the type of bushing that is installed in the regulator. You'll need that information shortly.
- [Optional] Reclaim other essential parts from old regulator. If you have purchased a new regulator, remove the two brass-colored wiring loom supports and two silver tinnerman nuts from the old regulator. These parts do not come with the new regulator and must be transferred to the new regulator.
Installation / Reassembly Procedure
- [Optional] Install the correct motor bushing for the application. If you have purchased a new regulator you will note that the unit comes with two small bushings – one plastic and one metal. This bushing must be installed on the new regulator before the motor is installed or the torque of the motor will eventually cause the teeth to mesh unevenly and destroy both the motor and the regulator. The proper bushing to use is based on the application and that is determined by looking at the old regulator. My regulator used the black plastic bushing, so I installed the new equivalent.
- Install and test the motor. Brush or spray on a bit of grease to the inner diameter of the bushing and then install the new motor on the regulator. Hand tighten the mounting screws until snug and then proceed no further. This is "by feel" and there is no torque spec. Then temporarily connect the wiring and blip the window button in both directions to test the motor. During this test, keep in mind that the motor is extremely powerful and they don't call them “scissor arms” for nothing. Keep all precious bits free and clear, okay?
- Transfer parts between old and new regulators. If you have purchased a new regulator remember to install the wiring loom supports and the tinnerman clips saved from the old regulator. While the wiring loom clips might be considered optional, the tinnerman clips receive the two screws located under the door pull to secure the door panel to the regulator and hence the door frame. If you don't realize those are missing until you've put everything back together you will need to pop the door panel free and peel up the insulation high enough to install the clips. Not the end of the world, but an easily avoidable hassle. If you are wondering why I make this point at all, let's just say I know how important it is...
- Install the new regulator on the door. Spray a bit of grease on the pivot bar slide rail. Then with the regulator arms AND the pivot adjustment bar INSIDE the door frame, mate the regulator to the door frame and secure it with the four bolts, washers and nuts. Optionally, apply a dab of removable (blue) thread locker to each bolt for extra security. Hand tighten to approximately 25 ft*lbs or until very tight (but not too tight...don't snap them!). Note that the forward-top fasteners may require repositioning of the regulator arms (upward, IIRC) to permit easy access. Reconnect the motor electrical connectors and move the arms as required. If you do move the arms up, make sure the window itself is fully up so the arms don't smash into it.
- Install the new slider pieces in the window rails. Actuate the window button to move the regulator arms down to the same point used to remove the old regulator. Carefully push the window evenly down into the door until the slide rails are visible. Clean out any old grease from the rails and then liberally coat the rails with new lithium grease. Insert one new slider clip in each rail, orienting them such that the open end of the metal u-shaped retainer clip faces toward the rear of the door. DO NOT REMOVE THE RETAINING CLIP FROM THE SLIDER as that will needlessly complicate reassembly and may ultimately sacrifice that part (only $4, but if you only bought two, you're screwed).
- Mate the regulator with the sliders. Fine tune the placement of the window, regulator arms, and sliders as necessary to mate them. Press the ball of each regulator arm by hand into the socket of the slider with sufficient force until you hear a loud click similar to the sound of tapping glass with the edge of a coin. The sound is unmistakable (and a little scary) but that signifies the arm is properly locked. If you simply press the ball in and it LOOKS like it's in, it's not. The loud click is critical. Listen for it.
- Teach the window motor its the new travel limits. Hop in the car and close the door. Then, pick a direction – up or down – and press the window button to move the window in that direction. Continue holding the button down after the window hits the physical stop for SIX SECONDS. When done, hit the button to move the window in the opposite direction and repeat the process. After you release the button this time, press the button again the opposite direction to activate the one-touch feature and test that the window moves up and down cleanly and quietly.
- Apply lithium grease to the teeth of the “gear” of the regulator. You will need to move the window up and down to expose the entire gear. The grease should coat both the teeth and about 1/2” of the outer face of the gear because a small green plastic spacer / bushing rides along the face of the gear and this will no doubt increase the useful life of that non-replaceable component.
- Finish up. Reinstall the insulation, airbag, and door panel, in that order.
- Have a fine brew, for thou art freakin' done!
Based on my experience the motor will fail completely in as little as one or two months following the start of any intermittent operation. As it is far easier to do this job if the motor works, even intermittently, take any intermittent operation as a glaring sign that you need to replace the motor as soon as practical.
Astute readers will no doubt point out that the technique I specify to remove the window motor in the case of a total failure could also be used to replace the motor even if it is working intermittently in order to save the hassle of disconnecting the regulator from the window and pulling the regulator out of the door. Provided you have sufficient patience to deal with the limited access and are willing to purchase the tools required to complete the task in that manner, I recommend you do it that way. All others, however, should follow the standard procedure and remove the regulator.
I believe those small, innocuous green plastic spacers contribute a lot to the overall rigidity and smoothness of the regulator and its motion. The new regulator moves the window a lot more smoothly and quietly, and lacking any other obvious damage to the regulator I have to suggest that these things do wear out over time. Shame too. The regulator itself is actually a solidly designed unit manufactured out of some rather thick steel.
Even if you punch out the center of the rivets required to remove the regulator, don't bother to drill out the heads. I tried one with a brand new drill bit and it didn't take long to convince me that the Dremel was the way to go. Keep in mind that this is coming from someone who has worked on airplanes and removed his share of rivets by drilling the heads. And by the way, only use reinforced cutting disks on the Dremel. The original cutting disks (typically the ones that come bundled with new Dremel units) tend to break very easily and throw shards everywhere...including your eyes if you're not wearing safety glasses.
There are a few tasks on the E36 BMW that I consider “rites of passage” and this is one of them. There are those who have replaced their window motors or regulators and those who will. I place this job squarely between replacement of the microfilter (not hard, just tedious and strange for the uninitiated) and a HVAC blower motor swap. But if you have the courage to tackle this task a significant DIY dividend is in the offering.