You can also check inside the power center to see how they are terminated, or look for the chassis ground point to confirm.
I certainly don't know for sure how your TT is wired, but I can tell you that in my new 5er, the battery wiring follows typical 110v household code, where white is neutral and black is hot ( positive )
Counterintuitive to DC wiring, where black is ground and Red is positive. Go figure.
If you hook it up backwards, it will blow the battery reversal fuse in the converter
Jim & Kim from Colorado
2014 Eagle 30.5 RLS
2015 Dodge 3500HD SRW 6.7L
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