The number 5 fuse controls the stop signal and the cruise control. I also controls the tach and the instrument cluster. Just for giggles replace the #5 fuse (white 8 Amp) fuse and see if it makes a difference?

I have 300plus posts on here and sometimes folks just do not know the answer. If thats the case your post will go unanswered.

The 560SL has quirks. A fuse change as I mentioned coulf fix your problem sounds ridiculous but the 5 fuse does affect the cruise control and the brake light. Who knows gofigure.

You are narrowing it down. it sounds to me you are either at a faulty light on dash or the fuse and bulb control is screwed up.

I blew a Fog Light last winter and replaced it this Spring and the dash light stayed on. I checked and the low beam was out. Replaced the low beam and found the fuse was replaced by an 8 Amp and it should have been a 16A works fine but also found out that I had two tail lights out and
I am still searching. There is something to using Mercedes Bulbs. I'm living proof but it only hold true for certain bulbs. Again, go figure!

Let me know what happens.

Last thing... Search the site for brake light controls, idiot light control on dash. See who answers these questions most often and write that person for direct help.

Hope this helps!

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1988 560SL
Black Pearl/Palamino