Where do I connect the ground wire in the fuse box?
 

First off. I have zero experience with aftermarket electronic accessories. I just bought a Garmin Nuvi GPS and I did not like the idea of using the cigarette lighter so I decided to hardwire it to my BMW X3 2004.

I found a fuse to connect it to but where do I connect the ground wire? I was told to look for a black bolt or screw. I do not see it anywhere. Anyone know where it is located? What does it exactly look like?

no idea, but with what I have wired in my X5 brown wire has ment ground.

I am not sure if I understand the question right - ground is ground, it is a metal part of a car that acts as a common plane for all the other electrical components. In other words, if you take an Ohm-meter, and put one end to the negative terminal of the battery and the other probe anywhere on the unpainted metal body of the car, you would have "zero" resistance. So, any metal screw, bolt or a nut that makes "naked" electrical contact with the body of the car should suffice. As a mater of fact, same Ohm-meter will allow you to determine if the desired bare metal part is connected to "ground" by checking the resistance between the desired spot and other known good ground, say, one of the nuts under the hood that hold the front shocks...

The power source for the Nav unit is a different story - you want to tap into "switched" positive power supply, that is "hot" when the ignition key is a position other than when a car is parked away. You don't want to have the battery drained while you are on a two-day business trip somewhere and your nav unit is powered all that time. Also, when you tap into a "switched" power line, you have to make sure that the additional load of the new appliance does not hinder the operation of the "native" device that is fed by that power wire. Otherwise, you might need to use a relay, to provide the unswitched power triggered by the "switched" weak wire...

I am not sure if my rambling made any sense... lol...

:)

my two cents...