Join Date: Jan 2007
Location: Allendale, MI, USA
Not to pick nits, but I don't think you have a 'short'. A short circuit would probably blow fuses or start a meltdown of some sort.
Sounds more like a poor connection somewhere, or a broken wire (yes, even if the insulation is intact they can break inside sometimes).
Wiggle the wire on the modulator in different places until you can narrow it down & find the faulty connection or wire. Tighten or replace it.
As far as the headlight, I would focus on the grounding first. BMW used the smallest guage wire for the ground possible, and I think it is too small. When I installed mine I ran a nice 14ga. wire to all the ground points, the ground in the wiring harness, and to a nice solid point on the frame as well. Better yet would be a direct ground wire to the battery. Of course recheck all the hot wire connections as well.