75A fuse blowing

[mytagsucks]

I know this is something really stupid causing the fuse to blow, any help would be awesome. I've looked at other threads related to this but nothing has been quite like this so I'm pretty stumped.

I have an sr20det and the alternator began going bad so I bought a replacement (for a KA as I've seen this works absolutely fine and has been done many times) and put it on. After the new one was on, I went to attach the battery. When attaching the negative, there was sparking on the terminal and the 75A fuse popped.

After this, I removed the positive cable from the alternator and replaced the fuse. No sparking, and the fuse remained intact. From this, I assumed the short was from the alternator itself and not in the positive cable. I then brought the alternator in and had it checked, passed with flying colors. From here I tried re-attaching the old alternator, that worked short-free before removal to see what would happen and it produced had the same effect.

Things I am sure of:
-The ground to the alternator is attached correctly (flatter end to the shell of alternator)
-The plastic o-ring to the positive terminal of the alternator is intact on both alternators and there is no contact of the positive cable to the shell of alternator
-11.7 volts measured from positive cable for alternator
-Also had the starter tested per recommendation of a friend, passed as well

What the hell could this possibly be? Its driving me nuts :mad:

[KiLLeR2001]

First off, Go Cubs.

Secondly, how does the alternator cable look/feel? There's a possibility it could have resistance in the wire due to excessive heat in the bay. This resistance could also be causing a low voltage of 11.7V to be read. My car right now is sitting at 12.36V.

You most likely have a short somewhere in the constant 12V power wires that come from the alternator cable to the driver's side fender well. I would check the harness underneath the driver side fender to look for any fraying of the wires. If everything checks out there, you need to go from that point of the harness all the way over to the fuse box.

It's a bitch but these wires are shorting out somewhere if the fuse keeps blowing.

edit: Also, I would hook up a 30A basic fuse or any fuse really each time you want to reconnect the negative cable so you don't keep wasting Nissan 75A fuses. Then if it doesn't blow the 30A fuse you have fixed the issue and can plug in your 75A.

[mytagsucks]

Thanks for the good advice, and yes go Cubs.

I've got finals all week so I'm hoping to get to tracing the wire asap, but I am also worried about potential damage to other electronic parts that could occurred because of this as well.

Without the Power attached to the alternator, the car cranks but won't turn over. This wasn't an issue before, and its leaving me pretty worried.

[solidsnake180sx]

This happened on my car when the alternator was going bad. Was popping the 75A fuse and car was running like poop.

Replaced the alternator with a remanned unit to discover that the "remanned" unit was actually bad too. Took it to an alternator shop afterward and now it works great.