A thought occurred to me...
I have a little blinky LED hooked up in such a manner that the V+ for my dash clock serves as the Ground when the power to the car is shut off, so that it blinks whenever the car is shut off, regardless of whether or not I turn my alarm on. But, as soon as the power is applied to the clock (key-on position) it loses its ground and ceases to function.

I was thinking...if you provided a large enough current to the chassis of the car (not sure how) would it be possible to defeat the grounding of every system? If this is so, it seems that it would be most wise to hook up ones alarm directly to the battery, eh?

 

So, basically; If you apply a sufficiently sized positive current to a ground circuit, will it cause it to no longer function as a ground?

 

mmm...
I would think that since your - battery terminal is attacked directly to the chassis, that this would prevent a 'backlash' of current to the other ground wires.

I guess....

Anybody else?