Brake light weirdness

timmyc · #1 10-31-2021, 02:16 PM

I decided to use the Mercedes Benz repair kit for the tail/brake light failure. I followed the easy instructions and started on the left (driver) side. Hardest part was trying to work around the GPS and CD Player. Don't do that. Just pull those out. 2 minutes. Got that side done but didn't have time for the right. All was fine then, maybe a few days later, I get "check brake light"? What?

I got into it yesterday. Checked the #9 fuse. Looks good. Continuity checks out. Got out the tools and started tearing into it. Yep. No voltage at the bulb socket? Voltage at the intermediary plug. What? Check continuity between plug and socket. All good. Same thing, though. NO voltage at the socket. Eff it. Cut the plug out and solder the wires together. Now I have NO voltage at the wire!?! Checked the fuse again and it's fine. The whole time, both center and right brake light work fine.

I back off when I get frustrated. Get the Foxwell out and see what the X has to tell me. Basic info. Then I notice "check side light"? Aftermarket LED that has been in for maybe a year. Okay. Could be coincidence it went out. Checked voltage. NADA! Alright. WTF?!

Here's where it get's really weird. When the #9 fuse is out, my brake lights still work!? Again. WTF?! So I put it away and am headed back out to try to figure this out.

With that said, anyone else ever run into this when using the M/B repair?

Thanks, all. Happy Halloween! I don't have cool pumpkins like EODguy. Check that out it you haven't!

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Effduration · #2 10-31-2021, 08:19 PM

What are you running for your tow hitch wiring?? Are you using factory harness or did you wire it yourself?

timmyc · #3 10-31-2021, 09:31 PM

Hitch is all factory wiring. Have not had any issues with that.

I've been doing a lot of reading and it sounds like it may be the LRM? Not sure yet and not sure how to diagnose that.

I'll report my findings/fix.

timmyc · #4 11-14-2021, 11:15 AM

It was the ground. For some reason or other, it worked for a few days then stopped. I had the lights on and pulled the ground from the post that is attached to the tail light and touched it to another post and it lit up.

I made a small bare spot on the metal around the post just to make sure I have a good ground.

Had nothing to do with the side light (halo). That was just a cheapo LED that went out around the same time!

Bdc101 · #5 11-14-2021, 04:24 PM

You mean the ground was corroded?

timmyc · #6 11-17-2021, 09:13 AM

Quote:

Originally Posted by Bdc101

You mean the ground was corroded?

No. With the kit, you have a new separate ground that you must affix to the chassis. My initial point of contact worked for just a few days, then I had to move it to the new post where I had removed some paint for better contact. Still no issues!

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