w115 turn signal relay problems

[luketmarx]

I've had recurring problems with the turn signals on the w115, and haven't seen a lot of resources online. I just learned something, so I thought I'd share. Feel free to chime in if you have more info on this topic.


The issue is the signal speed. They will work fine, then one day be super fast. It can be an intermittent problem, but it gets worse with time then stays super fast. It acts like you have a bulb out, but they are all working. Hazard lights also flash super fast. And sometimes they just fall off and stop blinking all together.


I've seen online if you replace the hazard switch it fixes this. In my experience, this does not.


There is another relay under the steering wheel, to the left a bit. You can find it by activating the hazards or turn signal, you'll hear it clicking. Pull it off it's connector, and your signal will stop. This is the culprit, the flasher relay.


Replacing this relay fixed my problem on my first W115 about 10 years ago. I've since gotten rid of that car and acquired another more recently, which developed the same problem.


I found a New-Old-Stock one on ebay, paid about $50 or $75 for it. I had taken my existing relay apart and attempted to replace some of the capacitors inside, and succeeded in making the relay stop working. I had also taken some three-prong flasher relays from an autoparts store and attempted to make one of those work, and failed as well, blowing lots of fuses. I'm sure it can be done but I couldn't make it work.


So, with this new relay from ebay it worked, but still was fast.


Most recently I discovered a flasher relay from a 1984 w126 300 SD plugs right in to my w115, with one problem. The blinker now works perfect, but my hazards no longer work. I'm satisfied for now, but welcome input on this subject. Thanks!