83 300sd brake light and turn signal electrical issues - PeachParts Mercedes-Benz Forum

eatont9999 · #1 06-17-2012, 03:49 PM

Hi again,

I started having an issue with my turn signals and brake lights last week after I broke my antenna trying to remove it. I don't think the antenna is required for brake light and turn signal operation but I have been surprised before.

The symptoms are when I step on the brakes, the gauges all shut off and no brake lights come on. The same thing happens when I activate the turn signals in either direction. Some times when I signaled, it sounded like a buzzing coming from behind the cluster. It wasn't coming from the door buzzer. Sometimes I will signal, get 3-4 clicks then nothing and the gauges go out too.

I have cleaned and greased the two chassis ground points in the trunk. I have cleaned and greased both tail light holders. I have replaced any burnt or corroded bulbs in the tail light assemblies. I went to PNP today and I got a turn signal relay from an 84 380SL and swapped it: same issues. The relay is a little different looking but I have read that people have used them.

I'm not sure what else I can check and where. I think it may be a ground issue but I don't even know where to start looking past what I have already done. I'm thinking of cleaning the ground points behind the cluster even though they look clean. Until I get this resolved, I can't safely drive the car.

Any help is appreciated.

eatont9999 · #2 06-19-2012, 09:49 PM

Update:

I cleaned and greased the ground points behind the cluster to no avail. I checked the fuse box once again and found that the (#12 IIRC) fuse was a crappy plastic replacement that had melted at the end. I cleaned the contacts and the fuse ends (replaced with a junk yard fuse). The problems have gone away and the brake lights and turn signals work as they should.

Even though no one replied but me, I hope this helps someone. If you have the time and a little sandpaper, go through your fuse box and clean the contacts on every one of the fuses and holders! Above all, Don't ever install those garbage plastic fuses from XYZ auto parts store. Buy the OEM spec fuses and save yourself the headache!

w123love · #3 06-19-2012, 11:53 PM

So this may/may not be related but have you done any stereo work lately? I had some very interesting things go bad when I replaced a head unit in my W123 wagon a month back.

I wired just one wire incorrectly, and my running lights would no longer work on the right side of the car. Also, the glow plugs would come on when I shifted into reverse, as well as the tach would go to ZERO when I pushed the horn in. Also, the instrument cluster lights would not work since I blew a fuse because of my wiring mistake.

I double checked my work, found where I went wrong, and everything went back to normal.

eatont9999 · #4 06-20-2012, 01:42 AM

Quote:

Originally Posted by w123love

So this may/may not be related but have you done any stereo work lately? I had some very interesting things go bad when I replaced a head unit in my W123 wagon a month back.

I wired just one wire incorrectly, and my running lights would no longer work on the right side of the car. Also, the glow plugs would come on when I shifted into reverse, as well as the tach would go to ZERO when I pushed the horn in. Also, the instrument cluster lights would not work since I blew a fuse because of my wiring mistake.

I double checked my work, found where I went wrong, and everything went back to normal.

I'm glad to hear you found the problem!

I have not even removed the radio head unit and it is still the original Becker. The radio never exhibited any issues during my troubleshooting. I have no plans to replace it, either. If I did, I would have no way to play my tapes. I do need to get it repaired, though. It started ejecting tapes right after they are inserted.