I'm doing the Big 3 on my truck right now since I have some leftover wire from my stereo install. I put the cable from the alternator + to the battery on a few weeks ago, no problems. This last weekend, I made up the ground cables from the battery - to the alternator bracket, and from there to the body ground. I started up the car and got a weird noise under the dash, fairly loud. A pulsating sound if you will. So I disconnected the body ground cable on the firewall, and it stopped inside. But if I put my hand on the cable going from the alternator + to the battery, you can feel a pretty strong pulsation in it, in a strange way it feels like energy "bursts" going through the cable, but I doubt it's anything like that. The only cable on it from the Big 3 right now is the alternator to battery, and it still makes this pulsation, although the factory alternator cable does not. If I put my hand on the alternator I can feel it strongly as well, probably about 6-8 pulses per second. The factory ground cable doesn't transmit these into the body, but I suspect that the 0awg cable is less flexible and will transmit this more. Is this normal or is their something wrong with my alternator, or worse yet, with my wiring?

 

I am assuming this is at idle? Does it go away with increased rpm?

 

Yes, it's at idle, haven't tried increased rpms. Will do shortly...

 

The pulse gets faster with rpms, and possibly a bit softer, but that may just be my mind playing tricks since it's faster.