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1998 SL500 CHAMPAGNE WITH MUSHROOM INTERIOR; 2007 ML500, 1976 450SL Project
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had the same problem with water. what I did I too the sam out, cleaned the PCB with contact cleaner really well, like 3 cans over a few days, inspect everything, put it back and test it for a month or two, then pull it out and coat the PCB with conformal coating liquid, by hand, in a few layers (no conformal in the connectors) The second fix was to relocate it to the side of the car, almost same level with the taillight so any water coming in would not reach it. and make sure the drain plugs are open; if no drain plug, make one.
did the same on the front SAM too, that had some corrosion too.
They work like a charm. Is unbelievable that MBZ decided to put the SAM in those places AND not conformal the PCB.
 

W163 Crash Test Driver
2008 ML350 (Me!), 2010 GLK350 (Wife), 2003 ML-350 (Deceased)
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You really need to fix the root cause. #1 suspect is that the taillight seals were installed incorrectly at the factory (adhesive stuck to the light housing instead of the body).

FWIW: I also found this interesting comment on the interwebs:
The water ingress into right rear inspection area where the fuse box is located was caused from the failure of a rubber washer that should seal the hole there the bumper fixing bolt comes through and is bolted from the inside. The fix is to remove the rear bumper and change washer. Mine was 32mm OD 5mm ID and 1.5mm thick.
Other suspects have been the high-mounted stop light, the right rear window seal, and one guy who had a leaking roof rail. You have to fix the leak though, one way or another. Otherwise water will continue to intrude and cause other problems, even with conformal coating.
 

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I just saw this thread. I posted some info on what happened to me on the other forum, but I did make 2 videos at the time. It turns out the root cause of my issues were related to sunroof drains. I highly recommend checking this, the water may not be coming in via the light seals like most people expect.



Hope that helps some!
 

W163 Crash Test Driver
2008 ML350 (Me!), 2010 GLK350 (Wife), 2003 ML-350 (Deceased)
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1,723 Posts
Wow, those videos are awesome! I don't think I have ever seen the rear sunroof drains exposed like that. I had no idea they had those weird boxes.

Thanks!
 

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Wow, those videos are awesome! I don't think I have ever seen the rear sunroof drains exposed like that. I had no idea they had those weird boxes.

Thanks!
I had no idea either, there was very limited info, it was a matter of tracing where water kept coming from. Initially I thought it was the seals from the top of the tailgate. However, when I pulled the headliner down I saw the water coming from further down. When I found the boxes I was kinda shocked especially that the top was open and filled with leaves. So if theres any issue even with a clog, the water will overfill over the boxes, leak down and it all channels due to the headliner design directly to the rear same. It goes in back to the pillar, into the foam, and then the foam leaks. Glad it can help some.
 

W163 Crash Test Driver
2008 ML350 (Me!), 2010 GLK350 (Wife), 2003 ML-350 (Deceased)
Joined
1,723 Posts
You know, I had a confirmed taillight leak some time ago and fixed it with new OEM seals. But every once in awhile I'll have my hands back in that area and think "Hmmm. This foam feels damp...kinda". Not wet exactly, but a little moist? I always blew it off as humidity, me being paranoid, or simply the way the foam feels. Now I wonder if I had/have two issues, and the same occasional leak as you (just not as bad). I may have to pull my headliner and check this weekend!

Great info!
 
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