For some reason, I was under the impression that the rear-most auxiliary port was live all the time. After attempting to connect my CTEK that does not appear to be the case.
I am used to using the O-ring adapter with my other cars to connect them to a CTEK (my 2010 E350 is still on its original battery!) but I don't get the sense that I can elegantly route the cables from the well-shrouded GLC battery under the hood to a convenient spot to connect my CTEK. I suppose my best option is just to use the jumper clamps? Not the most satisfying option. I am wondering if that is what everybody else does. Typically, I can find a youtube tutorial for everything but sadly nothing for the GLC. Should I just stop complaining and use the damn clamps?