Lito420,
I would be happy to send you the photos of the solder joint areas but this project was 4 years ago for me and I have had some computer hard disk problems since then which caused a loss of many files including photos. So I do not have photos to send. That said, I should also mention that the solder joints turned out to not be the problem that I had with my '98 ML320. The problem I was having with the lights was caused by a wire that had chafed all the way through. It was a wire that ran to the ABS hydraulic pump. The wire that chafed through was located behind the left side headlight assembly.
Did you also try replacing the brake light switch near the top of the brake pedal arm?
Ken

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2014 E250 Bluetec 4-Matic
2014 GL350 Bluetec 4-Matic
1996 Chevy Tahoe 4 x 4
2009 ML350 (sold)
2005 SLK350 (sold)
1999 E300 Turbodiesel (sold)
1998 ML320 (sold)
1991 300D 2.5 Turbodiesel (sold)