I have rebuilt many myself. They usually contain off the shelf components and are generally very "low tech". The biggest problem that I have seen is the fact that they use single sidded printed circuit boards. Vibration usually causes the solder joints to fail on the heavier components on the board such as relays and the like. Usually a good re-soldering will solve most of the problems. If they would have plated the thru holes the reliability and long term life of MB electronice would be much better.
Pop it open and have a look, you have nothing to loose.
I got too many cars!! Insurance eats me alive. Dave
78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k