1990 300SL Turn SIgnal Problem, Dash Lights Go Crazy
 

I hope someone has seen this already. The first time I use the turn signals the dash board warning lights all light up and some of the gauges go crazy for just a second. What is strange is the turn signals will work fine after using turn signals left and right once. Has anyone seen this problem? How is this fixed? Thanks John

fUSTER cLUCK
 

If the title offends, sorry. Try these guys for the bad cluster in your 129.
http://www.speedometershop.com/40year.htm

It is a not-uncommon problem that may be corrected by replacing a faulty electronic capacitor on the cluster's circuit board. It is simple to do, inexpensive, and many have done it themselves. See here: http://www.benzworld.org/forums/r129-sl-class/1266394-dancing-dash-light-more-question.html.

"Motherboard" failure is common on early R129 SL's. MB offered a replacement about 10 years ago...but no more.

You will have to have that one repaired OR replaced with a newer version cluster.

The cluster tools are a bit tricky to learn the first time. You can scratch or crack the plastic. It's better to drop the carpeted panel below the dash and push out the cluster from behind. Lower the steering wheel as far as it will go. Disconnect the battery. Slide a credit card or some other thin plastic tool around the edge of the cluster to break the "seal" with the cowel. Then gently push from behind. It's all electronic, so it will release from all the electrical plugs. Once you have it out, you'll see where / how to use the wire tool the next time.

Yeah,.... be REAL careful with the removal tool. The early R129 cluster has the attaching point at the back. Nearly 2 in. in from the front. Push the tool in 2.5" in on the side, turn it 90 degrees then slow pull it forward. It should catch almost immediately. The attachment point is near the front on the newer R129, after 97.....but follow the same procedure. If you don't you WIll slip and pull a chunk off the plastic lense.
And if it doesn't catch until near the front then slide something in on the side and push the padded dash to the side as much as possible. Then shine a light in to see if the tool has caught on the serrated plastic.
If you can't see it then push the tool all the way in and try again.
It isn't necessary to push it from behind....that's a real pain in the butt.
Just follow these instruction.
Now, anybody know where I can buy a front lense ??? I broke one.

I've seen a couple of replacement lens home-made from the flexible plastic you can buy at the hobby store. It's thin and easy to cut with scissors. Not original, but not bad either. Maybe these guys will sell just the plastic lens. Write them and ask. www.MBCluster.com

MBCluster only work on the cluster and instruments....not the plastic lense.
There are some guys in LA (North Hollywood Speedometer & Clock) that refurbish them and sell them for $150, plus they want your old one as a core.
Too much. $100 is a fair price.
Probably better off looking for a whole cluster for $150 to $200 and removing the lense.

Then at least you have some other spare parts.