PeachParts Mercedes-Benz Forum - View Single Post

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...