Driving the Jeep in for servicing today, following my wife in the SL, I noticed that the SL's brake light in the trunk lid is not illuminating when the brakes are applied.

Where should I start? Go to the dealer cause I am not handy? Or find a fuse box? I have not even looked in the owner's manual for tips yet.

Any advice?

 

90% of the R129 SL have that problem......There a wire broke in the trunk lid......The wires that they use are junk......broke on me 3 times......So I take apart my trunk lid and run new wires.......You can do it yourself and save a lot of money.......The reason the wires are broke is because people slam on their trunk......Try not to slam on your trunk......good luck.....

 

ChrisB

you can find the wires on the right trunk hinge. Its wrapped in a little tube.

If you get it fixed at the dealer, they will just use parts around to redo the wires... its not an "ordered" part so they get you on the "labor"

`fk

 

Thanks for the info . It sounds like I'm not the first that has had this happpen.

 

About 10 months after my original post and the repair having been done by a MB shop ... I noticed yesterday that the third brake light is out again.

This wil have to be fixed ASAP. Such an obvious deficency for a such a classy car just will not do.

We open/close the trunk lid about 6 times each weekend. Hardly ever durring the week. That does not seem like a lot.

MB must have done a poor wire splice job.

 

mine has been out for months now, too lazy to fix it. But I kinda like how the brake lights light up without it. In my opinion, with out the 3rd brake light, when you brake the car looks wider. :p

 

Another one I thought to myself.I checked with MB to see if a fix had been found yet for this obvious engineering fauxpax.What problem they responded!
After much experimenting and research,I discovered the engineering mistake.Yes I did say mistake.It is so simple.Any 4th grade science student would spot it 2 minutes.The problem is that the copper wires are attached inside a rubber boot inside the scissors hinge.This makes the wires and the rubber cover pinch every time the trunk lid is closed.Eventually the copper in the wires breaks and the brakelight fails.The answer was simple.Look to Honda of course.What else is new.Viola! The Accord had the exact same setuip except that they connected the rubber tubing to the outside of the hinge and had the wiring going up into the trunklid covering parallel to the trunklid,not at a 90 degree angle.So there are 2 solutions.Either splice the wires with a coiled wire so that it no longer bends, but moves up and down like a shock absorber,or have the spliced wires going out of the hinge cover straight to 1/2 way up the trunklid cover,thus eliminating the 90 degree bend in the wire inside of the scissors hinge.After looking at this for hours,I am truly amazed that the MB engineers came up with this system.Did they not look at a Honda Accord? I had a 1994 Accord and the trunklid light harness was done perfectly.All MB had to do was copy it.In fact the Nissan cars have it also.MB maybe the only auto company in the world that has this flawed system of running the wires through a scissors hinge.Whatever possessed them to do this I will never now.When you splice the wires,make sure you have plenty of wire length.You only want to do this once.Remember,no bends in the wire is your goal.

 

We had an A service done early last week. We had reported the third brake light not working.

The MB technician only checked the bulb function locally and reported the bulbs were OK. They did not think of or take the time to rework the wiring.

It always bugged me that the third light did not work. It looks cheap for such a fine car to not work properly for everyone to notice.

Rather than setting up another appointment, I finally set out to fix this myself today.

Jiffy knife, electrician's pliers, a 4 inch length of electrical plug wire, electrician's tape and 4 wire twist connectors in hand I tied into that rubber wire harness on the right trunk hinge.

One wire was broken, there was no evidence it had ever been spliced. So that "new" break was the reason for the recent failure. The other wire had been spliced previously by MB technicians and was in still in good shape.

There was lots of wire in cavity of the trunk lid that was easy to pull out to give lots of working room. In retrospect I could have done the job with two twist connectors and no new wire. But I was trying to get something more substantial in this hinge area to resist the tendency to break.

I ended up slicing the rubber wiring harness down the length to get it off and out of the way as I was doing my splicing job. In the end I re-installed the rubber harness and wrapped the outside of the harness with the electrician's tape.

I have not yet been able to get the bulbous end of the wiring harness back into the trunk port. It is bound in place by the trunk lid lining right now. I will need a different pair of pliers to re-insert that end. Any one know a trick for doing this easily?

About 40 minutes later ... the brake light was working again.

Not too bad for a guy who is not handy with such things.

 

lol. good job. My third brake light is out too, but I am too lazy to fix at the moment. It's been out for a looooooooong time now. To add to the third brake light, one of my hid bulbs is out too, again too lazy, just the one xenon on the passenger side is enough to light up the road.

 

Great info, just fixed my faulty third brake light. Broken wires just like everyone else. Cheers Guys.

 

I fixed mine a couple of years ago using more flexible wire, that turned out to not remain very flexible. The wire shouldn't attach inside the rubber boot if it's the way it came from the factory. The rubber boot isn't inside the hinge, but after it. There is a plastic cover before the boot that snaps over the hinge and the wire, with plastic pin fasteners. All the wire bending happens in the rubber boot away from the hinge (which doesn't get pinched but bends as intended). Like anything else, the wire will break over time. No engineering mistake.

 

Like always, this forum is dead on with issues and solutions...you have saved me countless amount of money on
DIY suggestions….my third taillight has been out for 6 months...I bought a replacement and installed, didn't work, so
I finally checked the forum here as there it was,..bent/broke wires at the right hand side bracket sleeve...I pulled apart, spliced together
and BINGO, issue solved!!! Thanks again guys for great advice.

 

Glad to help - I learnt the trick to this common problem on this forum as well.