Power window motor replacement

blkongry · 09:20 AM

Here's a little FYI info for ya'll. If you've got a window that goes up a bit, then stops and gives a "BRRRRR" noise, but then can be 'helped' up the rest of the way by hand, then you've got slipping gears in your power window motor. It's a little gear motor and the worm gear is so worn it's slipping past it's mate.

I had this happen on my '94 325ic and when I had the car in at my shop doing a clutch/tranny change, I had them look at it. They quoted something like $700-$800 to replace the whole regulator and motor assembly, which they said were both bad.

After choking on this price for a power window repair, I did a little diagnostics myself... it's all pretty straightforward, and it was obvious my regulator was fine. It was the motor that was slipping, so I got a newly-used replacement off Ebay for $60.

I knew going into it that the regulator is riveted on to the door frame, which makes sense since it's all assembled with robotics. I was told I needed to drill them out. Well, that's a b!tch because the rivets just spin in there as you drill, so I used a small fiberglass cutoff wheel and ground them off. If you grind the heads down to where you can just see a faint hint of an outline of the rivet, it will then punch right out.

If you look at the pic, there are 4 rivets to remove. Once removed, you can lean the regulator assembly out far enough to remove the star-head screws holding the window motor on (there are three of them). By leaving the rear trailing screw in the regulator (holding it to the frame at the far left in the pic), you can replace the motor without actually having to remove the regulator, but it's a PITA.

So, once you get the motor switched out, use some button head screws from inside the door frame to replace the rivets. If you use slotted head screws, then you can slip an screw driver in there sideways as you tighten the nuts. OH, and use nylocks on the nuts so they don't ever rattle loose. While you are in there, you'll probably want to grease your sliders.

This job pretty much sucked, for it means a lot of grinding, careful prying, and you've got to be a bit of a contortionist to get into some of the areas you need to, but if you take a couple hours, you could save several hundred bucks.

Lastly, if your window has problems rolling up, and it will stop at times giving off a nasty "BRRRR" sound, it's probably not your regulator, but rather your window motor itself.

Sorry this pic is a little blurry. I was so damn tired and greasy after the job I just snapped of a quick pic before reassembling... looked in focus on the little camera screen :-/

dboyles · 09-20-2005, 04:43 PM

Let's talk preventative maintenance: What causes the failure of the motor/regulator? The original owner of my car ('99 M3) had the assembly replaced under warranty at around 21k miles. I'm at 43k, and I try to use the windows sparingly because of this.

Can one lubricate the rubber tracks that the window uses when it slides up? Is that a job for Gummiphledge? I actually heard that it wasn't being made any more, and I seem to recall a substitute being mentioned in Roundel a few months back. What's everybody else doing to address this problem area?

blkongry · 09-20-2005, 09:02 PM

They make something called Silglide (not sure about the spelling) for the rubber tracks. White lithium grease is the best for the plastic tracks that sit in the riser at the bottom of the window, and heavy axle grease is the best for the main drive gear on the regulator and gear motor gear.

What can you do to keep them running smooth? Keep them clean, dry, and greased... and when i say them, I mean all the moving components. There isn't much you can do to prevent wear inside the gear motor, and that will just fatigue over time. What you can do to make the life easier on the gear motor is not hold down the up button when the window is at full extent... that just loads stress on the motor.

Just so you know, it seems that no one has perfected the power window... every manufacture has a similar and cumbersome design, and they all wear. But it's also an area that so many people don't think about... they lean on their windows, roll them up and keep holding the up button just to make sure it's alllll the way up. If your assembly has been recently replaced, it's aligned properly, and greased, then don't worry about using it them sparingly, just use them gently. For our rides, with the 'drop windows' on the coupe and convertible every time you open/close the door, I think that just adds tons of wear on our power window mechanisms... unfortunately.

dboyles · 09-21-2005, 08:06 AM

I had a '96 Honda that ate both driver- and passenger-side regulators, so I'm certainly familiar with it.

I've always figured the window action when you open the door was a contributor to the wear. At my Inspection II service (3000 miles ago) my mechanic (who knows his stuff) mentioned that my passenger window had a little "hitch" in it when going up, so I've tried to be gentle.