I did a little trouble shooting and the fan works great. But, I suppose something could be wrong and also not know? When I turn on the defroster the fuse for automatic air conditioning #3 gets beyond 160* and melts. I also have no bi level hi or lo function. I checked the servo and powered from an external source and it works. When I plug it in though it does now. I have several electrical diagrams etc.. but no clue how to read the blueprint looking stuff. Can anyone tell me (in simpleton context ) what places I should check in the system that would be suspect?

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Current fleet-
2015 BMW 750i xDrive
2009 BMW 535i xDrive
2004 Chevy Avalanche 4x4
1993 Mercedes 300SD
1993 Mercedes 300SE (parts car)

Previous Benz's-
2001 Mercedes SL500
1983 Mercedes 300SD
1980 Mercedes 300TD
1996 Mercedes E300D
1999 E300DT
1984 300TD-T
1988 Mercedes 560SEL (parts car)
1979 300SD
2003 E500
2004 S430 4Matic
2001 E55
2003 E430