My 124 sunroof works again!
 

In this thread I wish to say three things:
1. Some dealers are nice -- I specifically recommend Smothers European of Santa Rosa, California.
2. W124 sunroofs are way, way more expensive to repair than I thought.
3. MBCA memberships are well worth it.

The story
Due to a mechanic's error (a missing bolt) during the trap cat recall on my '87 300D Turbo (W124, OM603), a small oil leak occurred that I found and fixed at my own expense a couple of months ago. I mentioned my "concern" to the dealer's service manager but admitted that I could prove nothing and so omitted the usual screams and threats. In return, the service manager was kind enough to say that he would owe me a future favor. For once in my life, I was ready and jumped through the opening with "will you fix my sunroof?"

The deal
We negotiated a deal in which he would provide the labor free as "goodwill" and I would pay for the parts less 15% (MBCA discount). The car came home this evening (September 4) with a working sunroof. In the process, both the service manager and I got an education in what it takes to repair a 124 sunroof.

The sunroof
The W124 (first generation pop-up) sunroof is not one of Mercedes more robust designs -- many have commented here -- so I should not have been surprised by the mechanic's report, which went like this:

"Found sunroof not working, sliding panel painted shut, operating cable broken away from hold down clip and twisted. R and R headliner. Disassemble sunroof and inspect. Replace cable, guide tube, lifting bridge, water tray, guide arms both sides, update wind deflector, lifting/tilting mechanisms, various bushings. Adjust roof and recheck OK."

Parts is parts
They ended up replacing every part but the roof panel, liner, motor, switch, and wiring. Several parts were "updates" that hopefully will improve reliability. The factory sent some wrong parts the first time so the dealer had to re-order, thus taking longer than expected -- they had the car for a total of 9 "shop days."

Ouch!
Since I wasn't billed for labor, I don't know how many hours it took, but I do know that it was a lot more than expected -- I asked. Likewise, even with the 15% MBCA discount (which saved me $140 on this job alone), the parts set me back $870! Most of the parts are "dealer-only" and are expensive regardless of the source. I don't even want to think what it would have been with labor at $125/hour or whatever they are charging these days.

Thanks
I wish to thank those in the forum who advised caution, especially for folks like me who never saw a working 124 sunroof until today, much less taken one apart. For those of you who also have non-working sunroofs, especially those like mine, I recommend caution in opening this "can of worms." The best thing for the DIYer would be a donor car with a working sunroof so you can disassemble and learn as you go.

Jeremy

A donor car sunroof can be removed in one piece, without disassembling. Could be a handy parts source, visual aid, or one-piece donor. The most difficult part of this is the headliner re-securing without wrinkles.

Glad it went well Jeremy, a properly functioning sunroof is IMO a big plus on a car.

After my wife accidentally activated my semi-functional w124 sunroof, it was all I could do to get the damned thing back down again. After that event, I disconnected the wiring. That thing will never open again so long as I own the car!

Dan, I hear you. If I had not lucked into the special deal I would have left my sunroof broken like yours.