Chattering Sunroof Motor That Works Manually

[Bmrlvr4lfe]

Hey All
87 325is
Automatic Sunroof

On my 3rd sunroof motor
Sunroof works manually but chatters and doesn’t move when using the motor
Rails have been cleaned and lubed
No broken parts
New motor cog
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Could this be a sunroof cable issue?
I’ve adjusted the 21mm nut many times both ways, tight it chatters and doesn’t move manually, loose it doesn’t chatter but motor works with no chatter but doesn’t move sunroof, its in this position I can move it with the hex wrench.

Bought the car as a roller so I don’t have any history on repair.

I would really appreciate it if someone could provide some insight for me. I don’t want to spend the $200+ for cables if it’s not the issue. Thank you!

[strickland]

These things are a pain. I’ve had mine apart about 50 times.

When you say it moves manually, do you mean it cranks with the allen key by hand?

so many little elements in the arms, track, etc. can all affect the smooth ride of these rails & cables.

The rail system also benefits from spit-shine cleaning. Gunk builds up & it all makes a difference.

[Bmrlvr4lfe]

Thanks for the reply! Yes it moves fine with the Allen key. Thats what baffles me, if it moves straight and smoothly with the Allen key manually, why won’t the motor move it?

I’ve cleaned and regreased the rails, cables and components. The motor worked fine when I tested it before installing. I’m running out of things to do.

Im going to pull those cables/splines out and really clean them well. I just don’t want to make things worse by breaking something or not aligning the cables correctly.

Thanks again!

[strickland]

It's a lot of trial and error and cursing. I have gone thru these exact issues, learning as I went. Happy to share what I learned...... you asked for it!


My guess is that the chatter indicates some sort of unwanted friction, which is causing it to 'jump' rather than move smoothly.

If the teeth on the motor cog are good, I doubt you need to remove the cables. (Re-aligning that stuff is do-able, but also required a lot of trial and error. More on that later, if needed.)

Helpful troubleshooting method I found... which you may already be doing... is to run the system without the sunroof panel attached. Keep the arms, tracks, etc all in place. Standing outside the car, I could reach my hand into the sunroof hole and push the buttons to run it back & forth. This way, I could observe everything from the top and look for issues.



OK—Two tiny things come to mind:

• The first is the spacing under [whatever this thing is called--red arrows below]. I found that these screws could be over-tightened, causing the channel to be too narrow. Loc-tite is your friend when re-assembling this system. Over-tighten these screws, and the system bogs down (possibly with a chatter).
  
  There was a sticky piece of stock cloth tape (?) under there, which I discarded during my process. Later I wondered if that .5 millimeter of spacing made a difference in allowing ample room for movement.

• The second possibility are these annoying little tabs on the sunroof arms, which help keep everything aligned. They also trigger the wind flap arms.
  
  Mine broke off, and it took me a long time to realize that they were somewhat critical.
  
  I wound up using some used parts from an earlier car (mine is post facelift, 89). I found that these little tabs were slightly different, and I had to make a repair here. Fortunately, I had saved everything and I still had the broken piece from my original (late model) sunroof arm.

WHEW good luck, amigo! I'll be curious to find out what finally solves it!

[Bmrlvr4lfe]

Wow! Thanks Strickland!
I ended up not pulling the cable’s after deciding
the process of putting them back together might do more harm than good. I did check and make sure that any cable I could see was clean and not worn.

The information about the torque on the screws is very helpful and I’ll look for those clips that might be broken. I’ll remember the trick about watching it run without the panel on the next time I pull it apart.

I did find that the wind visor was causing some interference when closing and opening. I pulled that and found that it wasn’t seated properly in the middle and there was some over lapping headliner fabric causing it to sit higher than it should.

I have it all put back together and the motor is moving the panel! (Yes!) Just have to get that darn interior sunroof panel back in place. I tried until I gave up in frustration last night, the part that had the clips is a pita to get over the front part of the panel!!

Thanks again for sharing your experience, it helped a lot and I’m sure it will help many others both now and in the future! 🙌🏻


Ben

[strickland]

Hell yeah brother! Glad to hear it is improving. IIRC, I re-clipped the interior sunroof panel when the sunroof was halfway back.

I’ve taken mine apart too many times to count, and happy to share my hard-won knowledge. That’s what this forum is all about. 😎