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Premium Member
2021 GLC300 and 1987 560SL
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3,617 Posts
Discussion Starter · #1 ·
I got a right license plate light out error a couple of days ago. This evening, I replaced the bulb - and the new bulb turned on immediately when I snapped it in place, and stayed on regardless of what I did. Start the car, stop the engine, turn it off, take the key out, cycle the light switch, nothing. I wound up taking the bulb back out so it didn't run my battery down.

Any thoughts on what might cause this?
 

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Premium Member
2021 GLC300 and 1987 560SL
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3,617 Posts
Discussion Starter · #3 ·
Did you buy a 6418 Long Life bulb?
Think that's what I have. I bought 5 of the right bulb from AutohausAZ a couple of years ago, after the ones I could get at my local auto parts stores kept burning out in my previous 210 wagon. I've used one previously on the left side on this vehicle.
 

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Outstanding Contributor
2006 ML500 2002 ML320
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Think that's what I have. I bought 5 of the right bulb from AutohausAZ a couple of years ago, after the ones I could get at my local auto parts stores kept burning out in my previous 210 wagon. I've used one previously on the left side on this vehicle.
You are supposed to be using Sylvania/Osram 6418 LL bulbs. Any automotive store has them.
 

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Premium Member
2021 GLC300 and 1987 560SL
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Discussion Starter · #5 ·
You are supposed to be using Sylvania/Osram 6418 LL bulbs. Any automotive store has them.
Just looked. Yup, that's what these are.

But even if they weren't, that wouldn't explain why it's stuck on all the time...
 

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2006 ML500 2002 ML320
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The rear SAM controls the Lic. Plate light, but there are no wiring diagrams for lighting.

Have you had water entry in the rear cargo area or did this problem start following a heavy rain?
 

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Premium Member
2021 GLC300 and 1987 560SL
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Discussion Starter · #7 ·
The rear SAM controls the Lic. Plate light, but there are no wiring diagrams for lighting.
I was afraid of that...

Have you had water entry in the rear cargo area or did this problem start following a heavy rain?
No and no.
 

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Outstanding Contributor
2006 ML500 2002 ML320
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I was afraid of that...


No and no.
I am not saying that the rear SAM is the problem and that it should be replaced, but I strongly urge you to remove the spare tire and everything else including the grey mat.

Then you will find the rear SAM, the tailgate control module and the tailgate pump. Open the pump cover and see if there is corrosion. If there is, there is a good chance the the rear SAM has been affected.
 

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Premium Member
2021 GLC300 and 1987 560SL
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Discussion Starter · #9 ·
Well, when I pulled the molded tool carrier out, there was water on the underside...so I guess I've got a leak.

Is it possible to pull the SAM and inspect it and clean it up without causing problems? Or am I doomed to take the car to a dealer and fork over a couple of kilobucks for a new SAM?

And of course, it's time to do something about the taillight seal...
 

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Outstanding Contributor
2006 ML500 2002 ML320
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Well, when I pulled the molded tool carrier out, there was water on the underside...so I guess I've got a leak.

Is it possible to pull the SAM and inspect it and clean it up without causing problems? Or am I doomed to take the car to a dealer and fork over a couple of kilobucks for a new SAM?

And of course, it's time to do something about the taillight seal...
Key in hand, remove Neg. battery cable and remove rear SAM. Then take the covers off and spray board with Electronics Cleaner.

Also open the Tailgate Pump and look for corrosion.
 

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2021 GLC300 and 1987 560SL
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Discussion Starter · #11 ·
Well, my SAM isn't water damaged at all. I got it out, pulled it apart, and the board looked pristine. I put it all back together and lo and behold, the right license plate light works correctly.

I do have water in the bottom of that compartment, so I'm pretty sure it's an ingress issue. What's the right fix for the taillight seal? VIN is 4JGBB22E48A369680.
 

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2006 ML500 2002 ML320
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Buy both seals from the dealer. Remove the tail lights and you will see that the seals were adhered to the tail lamps instead of the body because the glue was manufactured on the wrong side.

Clean everything off of the lamp and carefully place the seal over the body cavity, then reinstall the lamp.
 

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2021 GLC300 and 1987 560SL
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Discussion Starter · #13 ·
Ordered both seals. $78 from FCP Euro for genuine Mercedes, with two-day shipping. I wasn't about to get the Üro crap for this job.

The good news is that it looks like a 30 minute job, once I get the seals in.
 

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2021 GLC300 and 1987 560SL
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Discussion Starter · #14 ·
Yeah, it's a 30-minute job. Four nuts, easy to get to, and hte lamp assembly slides out. Be sure to unplug the main connector and, if you've had the direct wire fix done to your lights, that connector as well, before pulling the assembly free.

And I can see why the gasket needs to be stuck to the car body, not the lamp. One question: does the small oval gasket on the side need to be done the same way?
 
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