84 300CDT sunroof won't budge - PeachParts Mercedes-Benz Forum

rcounts · #1 05-28-2008, 02:55 PM

I already searched for info on sunroof problems but couldn't find a description where anyone had a problem quite like mine so I decided to start this thread.

I started working on my sunroof - which has not worked since I got the car - and I discovered a few interesting things. I wanted to share them and find out if what I have found is normal and if anyone has suggestions on how to fix it.

First, the really minor issue. The switch works the opposite of what I expected it to. Pushing on the upper part makes the sunrof OPEN and pushing on the lower part makes it close. Is this normal, or is something wired backwards? Would reversing the leads to the motor fix this to make it operate more intuitively - instead of backwards of what you expect?

Now for the big problem. It won't open, and here is what I've done so far.

I pulled the rear tube off (after the motor/gearbox) to expose the end of the cable. When you activate the switch to close the roof the end of the cable disappears into the gearbox and appears to pass all the way through it - and then you can hear it after the end of the cable passes the gears - it makes a ratcheting sound. Is this normal operation - for the cable to go all the way in until the end goes past the gears?

When you activate the switch to open the roof the gears grab the cable and pull it until about 1 inch is sticking out past the gearbox and then it just stops dead. The sunroof panel doesn't budge and the motor stops turning (not a slipping clutch). I had my kid working the switch from closed to open repeatedly while I pushed down on the front and back edges of the roof panel and it still wouldn't budge.

When you work the switch to open it, you hear the motor run a second until the cable pulls tight and then that's it. No more noise at all. When you work the switch to close, after a second, you can hear the gears turning against the end of the cable that has gone past the gears - it makes the ratcheting noise I mentioned earlier.

So, next I tried using the manual crank in the trunk with a socket and ratchet. Guess I cranked too hard on it because the plastic cap just stripped out - no help, no movement of the sunroof.

At this point I though there might be a bent wrap or something on the cable that wasn't meshing correctly with the gear teeth - so it couldn't feed through the gearbox past that point - causing it to jam. I removed the motor and gearhead assembly and examined the cable. No signs of any damage or any wire wraps mashed together or anything that would bind up in the gears. No sign of problems with the gears either

So, next I grabbed the cable by hand (I am afraid to use a tool for fear of damaging the cable) and I pulled it as hard as I could. No sign of it even ACTING like it was trying to budge.

I have seen mentioned in other threads that there is a "pivotable locking mechanism in the roof itself that has to be pulled back then the roof is retracted". It is described as being at the FRONT of the sunroof opening and attached to the cable with a clip. Is this the main attachment of the cable to the sunroof panel, or does the very end of the cable attach to the panel separately? I ask because the cable is still very FIRMLY attached to something, but I don't know if it is still attached to the panel and detached from the locking mechanism - or if they are one and the same attachment point. If the lock were only attachment point - and it was detached - the cable should slide out, right? So I'm thinking it must attach at two different points to the lock and to the panel separately and it is still attached to the panel, but not to the lock.

If that is the case then it seems like maybe this locking mechanism isn't unlocking. Anybody got any suggestions on how do I get at it? How about dropping the headliner - without damaging it - to get to the mechanism. Is that possible? Any ideas?

My latest idea is to see if I can find
1) a hardened spring that is just the right wire diameter and coil size to "thread" it onto the end of the cable an inch or two
2) a wood screw with an eyelet type head with the right shank size and threads to screw into the open end of the spring
3) a small turnbuckle that I can attach one end to the eyelet and the other end to one of the sheet metal braces for the bumper mount inside the trunk

By turning the turnbuckle I should be able to put a steady firm pull on the cable - without damaging it - and just see what happens.

Sorry this is so long, but I'm hoping someone will take the time to read it who has had the same or similar issues and can offer some guidance. I'm pretty much at a loss for what to try next at at this point...

bgkast · #2 05-28-2008, 03:02 PM

It sounds like your gearbox or teeth on the cable are stripped and your cable may be binding.

I would try pulling out the cable, follow this procedure I made up: http://www.peachparts.com/Wikka/W123SunRoofRepair

rcounts · #3 05-28-2008, 04:21 PM

Quote:

Originally Posted by bgkast

It sounds like your gearbox or teeth on the cable are stripped and your cable may be binding.

I would try pulling out the cable, follow this procedure I made up: http://www.peachparts.com/Wikka/W123SunRoofRepair

Thanks for the reply. I actually looked at the article you wrote already - nice job by the way. Unfortunately, I think you missed part of my original post (no wonder with it being so long and all) - here's the part I'm referring to...

Quote:

...I removed the motor and gearhead assembly and examined the cable. No signs of any damage or any wire wraps mashed together or anything that would bind up in the gears. No sign of problems with the gears either

The cable and gears appear to be fine. With the cable out of it and the main drive gear removed, the teeth that engage the cable all look fine. The cable just won't move to pull the sunroof open (not even halfway) so I'm not sure that the info in your article applies in this case.

Is it possible to pry the interior panel securing clips out of the outer roof panel, drop the interior panel, and slide it back out of the way WITHOUT opening the sunroof first - and without damaging the interior panel?

Do you know anything about the roof panel "locking mechanism" that others have referred to? In looking at your article I didn't see anything in the pictures that fit that description. I'm wondering if I can get the interior panel out of the way, maybe I'll be able to see it and unlock it.

bgkast · #4 05-28-2008, 04:31 PM

Reading your post again it sounds like your cable is too short. When the roof is all the way closed the cable should still be sticking out of the back of the gearbox a bit, and you should not be able to remove the tube at the rear of the gear box due to the cable extending into it slightly.

This lock mechanism is simply the cross bar that the cable attaches to as seem in pictures 3,4,10 and 11. The cable pushes the roof closed, then continues pushing a bit to raise the back of the panel.
If you can get your roof open a bit then pull the headliner off and take a look; if you can’t try popping the clips at the front off and gently pull down in the center of the headliner at the front and rear to free the sides (into a taco shape). To remove the headliner with the roof closed you may have to sacrifice the headliner...

rcounts · #5 05-28-2008, 05:12 PM

Quote:

Originally Posted by bgkast

Reading your post again it sounds like your cable is too short. When the roof is all the way closed the cable should still be sticking out of the back of the gearbox a bit, and you should not be able to remove the tube at the rear of the gear box due to the cable extending into it slightly.

Interesting. How could it be too short? The cable has a finished end - just like the one in your pictures - so I know the end hasn't broken off. Since mine is a coupe, I would at least think that the cable from a sedan would be too long rather than too short, and the cable out of pretty much anything else is just going to be all around wrong...

Quote:

Originally Posted by bgkast

This lock mechanism is simply the cross bar that the cable attaches to as seem in pictures 3,4,10 and 11. The cable pushes the roof closed, then continues pushing a bit to raise the back of the panel.
If you can get your roof open a bit then pull the headliner off and take a look; if you can’t try popping the clips at the front off and gently pull down in the center of the headliner at the front and rear to free the sides (into a taco shape). To remove the headliner with the roof closed you may have to sacrifice the headliner...

Yeah, my roof won't open AT ALL right now. If I can "taco" the sunroof headliner panel enough for the clips to come out of their holes, it should slide back out of the way - shouldn't it?

Now I'm wondering if I could have this problem

Like the guy in this thread
http://www.peachparts.com/shopforum/diesel-discussion/149549-still-stuck-78-300d-sunroof-pictures-attached.html#post1132634

If the outer "sleeve" is misaligned like his was then
1) it isn't going to slide over the cable "shell" like it should so pulling on the cable wouldn't open the roof, and
2) that offset of the two ends would make the cable appear that much shorter at the motor end - just like what I'm seeing.

This is starting to make more sense. If that is the situation, then if I can unclip and slide the inner panel back out of the way, I should be able to get hold of the outer sleeve and move it around enough to align it with the cable shell. At that point I should be able to open the roof. Once it is halfway open I can then take get the inner panel all the way out so I can actually see the area at the back of the panel where the sleeve and shell are supposed to meet. Then it is just a matter of figuring out how to repair the misalignment of the sleeve and shell and hold them in alignment so the problem doesn't happen again.

So I guess that is my plan of attack. Thanks man - by just answering the question about how much cable should stick out of the motor assembly when the roof is closed, you may have put me on the right track to fixing it. TOO COOL!

bgkast · #6 05-28-2008, 05:56 PM

Hmm, that misaligned tube sounds likely. I had not seen that problem before.

rcounts · #7 05-29-2008, 01:17 AM

Well, as it turns out I have the exact same problem as the picture posted above - only a little more extreme.

I used two butter knives to gently pry the sunroof headliner panel down at the front until I could get my fingers in on top of it. A little bit of a tug and the clips popped loose one at time. Once all the clips were loose I was able to bow the front edge down and slide it right back out of the way.

At that point I could see that the shell had indeed slipped out of the sleeve and they were misaligned nearly two inches.

I unbolted the cable bracket at the front and removed the two 8 mm bolts ate each end of the crossbar, and lowered it down. I pulled the cable retaining clip out of the bracket and slid the bracket, sleeve, and crossbar off the end of the cable. I was then able to open the sunroof far enough to remove the sunroof headliner panel.

Next I pulled the cable all the way out of the shell and examined it. It had a pretty good z-bend in the cable but I was able to straighten it up pretty well. Several of the 1/2" pieces of clear plastic and the white plastic "beads" on the cable were a bit chewed up - about 3"-4" of cable length worth. I cut and removed the damaged ones, then took an old piece of motorcycle clutch cable I had lying around and stripped the plastic off it, and cut off a 4" piece of the coiled flat-wire shell. I grabbed the two ends of the 4" piece and stretched it to almost twice its length to open up the spaces between the coils.

Then I took the piece of shell and spiral wound it around the section of cable that was missing the plastic sheathing and beads - which is the same section that still had a couple of very slight kinks - caused by the shell/sleeve misalignment. It was REALLY hard to get it around the cable and when it was done it ended up being just a tad smaller in diameter than the plastic beads, and just a little stiffer than the main length of the cable.

I started to try to put the cable back into its shell, but it would only go back in there about a foot or so before it stoped and I couldn't get it to go in any farther. The "geared" part of the cable seems too stiff to navigate around the bends in the sheath very well. I'm wondering if I might have better luck running a piece of thin strong wire in from the trunk end of the shell and pulling the cable through?

Anyway my kid had a baseball game that I didn't want to miss, and I had to stop at this point. So I slid the sunroof panel closed and bolted the crossbar back into place. I then wedged a couple of plastic bottle caps in under the rear corners of the sunroof panel (on top of the tracks) just to make sure it stays closed until I get the chance to finish the job. All that is left now is to put it all back together - once I figure out how to get the cable back into its shell. Any helpful tips in this area would be greatly appreciated.

bgkast · #8 05-29-2008, 02:02 AM

You should be able to push the cable through the guide tube from the sunroof side back towards the gear box. I was able to do this when I replaced the worn cable in my first 240D, the toothed section should go around the bends fine. You may want to use a bit of grease and twist it as you push. Are you sure it's not just hitting the gear box? Once you feel it hanging up try pushing on the cable and pressing the "open" button.

rcounts · #9 05-29-2008, 02:25 AM

Quote:

Originally Posted by bgkast

You should be able to push the cable through the guide tube from the sunroof side back towards the gear box. I was able to do this when I replaced the worn cable in my first 240D, the toothed section should go around the bends fine. You may want to use a bit of grease and twist it as you push. Are you sure it's not just hitting the gear box? Once you feel it hanging up try pushing on the cable and pressing the "open" button.

Ummm, like I said, it is only going in about a foot (presumably to the first bend) and it stops. It took a pretty good tug to get it out past the bends too. I lubed it up good with grease, and tried turning it while pushing it in, but it isn't that easy to twist, being all greasy and everything.

rcounts · #10 05-30-2008, 11:16 PM

Well, I finally got the cable back into the shell and got everything put back together. Opened and closed it a couple of times and the sleeve slid past the shell and hung up again. I got to looking at it and figured out the problem.

At some point the clutch must have been adjusted WAY too tight and when the roof hit the stops while closing the pressure pushed the shell backwards so hard that the flat tabs welded on the shell - the ones that connect to the rear bow with 2 bolts - broke off the shell tubing. Once the tubing was no longer held in place by the tabs, it was free to slide to the rear - bending the existing gradual bends in the tube even farther and sharper. That's why the fatter "geared" end of the cable was so hard to push back in past the bends - they are sharper bends than normal.

So the only way to fix it "right" would be to drop the headliner and replace the cable shell with a new one that has the mounting tabs on it. HOWEVER, I came up with a much simpler alternative. I went to the hardware store and got a couple of 1/4" cable clamps, a couple of 2.5" long 5/16" bolts, and a couple of 5/16" rod couplers (a.k.a. "high" nuts)

I took the two saddles from the cable clamps and ground them down to where they would fit face to face with the 2.5" long bolts to form basically a split block that would clamp onto the cable shell.

Next I used a couple of blocks just the right size to block the roof panel up so that when I activated the switch to open the sunroof it couldn't drop and retract. That way the motor pulling on the cable pulled the cable shell forward to where it slid into the sleeve attached to the roof panel about an inch - far enough to keep it from ever sliding out and getting the ends of the tubes misaligned and hung up again.

Then I fitted my clamp around the cable shell and threaded the rod couplers onto the bolts and screwed everything together finger-tight so that it would just barely still slide on the sleeve. Next I got a regular socket that would fit the bolt heads and a deep wall socket that would fit the rod couplers. Using about 2 feet of extensions and a universal joint on each socket I put the sockets on the bolt head and rod coupler and used the extensions to push the clamp all the way back until it was against the front side of the roof bow that the shell used to be bolted to.

Once I had it in place I tightened the bolts on both sides of my home-made block clamp. Once it was all tightened down, I removed the blocks that were holding the roof "locked" closed and gave it a try.

VIOLA' the sunroof opened and closed as it should and the clamp kept the cable shell from backing out of the sleeve on the roof panel. Once it was all working well, I backed off the adjustment on the gearbox clutch so that it still moves the sunroof panel just fine, but when it hits the fully opened or fully closed position the clutch starts to slip instead of trying to tear something up.

The only drawback to this "fix" is that since there is now a clamp around the cable shell, the sleeve attached to the sunroof hits the clamp instead of sliding until it hits the crossbar behind it. So it doesn't open quite as far - it opens about an inch less than it would without the clamp. Not a perfect solution, but compared to having to remove the headliner - and possibly remove the rear window to get the headliner out of the way - I can live with it!

So friends, the moral of the story is DON'T OVER-TIGHTEN THE CLUTCH ON YOUR SUNROOF MOTOR!. Adjust it just tight enough to move the roof panel without slipping, but still loose enough to start slipping when it reaches the fully closed or fully open position.

jkoebel · #11 05-30-2008, 11:19 PM

CDT? You have a turbo coupe-wagon?

bgkast · #12 05-30-2008, 11:47 PM

You could always swap in a manual roof.

turbobenz · #13 05-31-2008, 12:28 AM

Swapping in a manual sunroof would be 100x harder than rebuilding the elctric sunroof. it is actually a really simple design. Once you get it all back together make sure you adjust the clutch to the point where if the car is silent and you open it all the way or close it you should still here the motor turning and struggling. If it doesn't keep turning after the sunroof is closed fully or opened you'll eventually strip the plastic gear

rcounts · #14 05-31-2008, 05:40 AM

Quote:

Originally Posted by jkoebel

CDT? You have a turbo coupe-wagon?

300CDT = 300 CD Turbodiesel

Quote:

Originally Posted by turbobenz

Swapping in a manual sunroof would be 100x harder than rebuilding the elctric sunroof. it is actually a really simple design. Once you get it all back together make sure you adjust the clutch to the point where if the car is silent and you open it all the way or close it you should still here the motor turning and struggling. If it doesn't keep turning after the sunroof is closed fully or opened you'll eventually strip the plastic gear

Yeah or you'll end up having the mounting tabs on the cable shell break off - like mine did.