Using either of the switched power sources will NOT cause problems with the CAN-Bus system because the only thing connected to it would be the relay which turns on/off the draw to the fuse block. Your fuse block does NOT take its power from the switched power source! It takes it directly from the battery, controlled by the relay which itself draws so little power that it doesn't affect CAN-Bus.
I do suggest that you don't use anything "always hot" as one day you're going to forget about it and come back to a dead battery or worse. I run my heated gear (jacket and gloves) through my fuse block (switched) as well as an air compressor for the tires. No problem at all. And of course the little stuff - GPS, most lights, etc.) are even less problem.
Originally Posted by Gumbeaux
Good stuff. Thanks! Hell, I forgot I bought one of those BMW pigtails some time ago...just found it in the toolbox...gonna wire it up and add the Fuse Block.
If using either of these CAN-Bus switched power sources (the BMW or the TT) plus a Fuse Block, are we still subject to the "Canbus might shut it down if it is too much draw" situation?
Without a full blown analysis of wattage here:
Scenario: heated vest plugged to outlet, GPS running on Fuse Block (switched source), LED lights running on Fuse Block (switched source), possibly one other warming accessory linked to Fuse Block (always hot, with an on/off switch on the accessory itself).
Would CAN-Bus go nuts in this scenario or is it only "seeing" the power draw from the directly connected stock plug?