W116 sunroof switch repair

The sunroof on my 280SE has not worked properly since I bought the car.    It would sometimes move a bit, if I played with the switch, but not often.   Since I didn’t want the roof stuck open, I didn’t use it.   Based on that, I figured my issue was the W116 sunroof switch.

The car is booked in for the Shannons auction in May, so I wanted to get the Sunroof working.   I don’t use sunroofs a great deal, but they are not common on the W126 280, so its a valuable feature on my car to be working.   I had sourced what I thought was the right switch, so I figured a simple matter of just fitting it.

Removing the old switch was somewhat of a pain, as one of the tabs that holds the switch in place was bent out too far.   In the end I got it out, and promptly lost the plug in behind the dash.   I was able to reach it again by removing the demister switch and using a hook tool.

This was also required to get a finger in behind the plug, so push the switch on.    Straightaway, I had a problem.   The new switch was reversed from the old one.   I could open the roof with the close side of the switch, but not close it.  I’ll have to compare it, but I may have a C107 switch.

At that point, I figured I would have to persevere with my old switch.   I gently took it apart and found it quite dirty inside.   The old grease had become quite sticky.   The switch is quite simple, it pivots on two very small ball bearings, and pushing down makes a contact with a metal bridge and the body of the switch.    I didn’t take a photo as I didn’t want to drop the small parts out of the W116 sunroof switch.

I used some brake cleaner to clean the parts up.   Quite a lot of dirty gunk came out of the switch.   I didn’t re apply grease, as I didn’t have one suitable for electrical connections.     Once I plugged it all back in, the sunroof finally worked.

While I was there, I also wanted to fit the new SLS control rod that had arrived in the mail.   The old one had broken bushings and I temporarily held it on with some cable ties.   That hadn’t worked, as only the very inner pin of the each end of the rod was still present!   I’ve already covered setting the proper ride height of this system.    The system on the 280SE was working perfectly as the arm changed the ride height as it should.

Finally, there was some minor rust around a door drain hole.  I treated it with rust converter and painted it, to ensure it didn’t get any bigger.   Unusually for a W116, as far as I can tell this is pretty much a rust free car.   I didn’t want that to change.