New KA alternator installed in my SR is causing a short, need help

[wadiad]

Hi, i could really use some help particularly from those of you who are familiar with installing a KA alternator in the SR.

I installed a rebuilt high-output 1990 240sx alt. in my redtop sr20det, and it seemed like a straightforward swap (2 wires and a plug to connect), but i've apparently messed up somewhere. When i reconnected the battery, it sparked a LOT, i blew a 100 amp fuse and the starter wouldn't work. I don't know what that fuse is, but i believe it's the only 100 amp in the car. Regardless, i replaced the fuse and attempted to reconnect the battery ground but stopped when it began sparking a lot again. I contacted someone local and told them i had reconnected a black wire to the alternator housing, which is how it looked to be connected on the stock alt. He told me the alt. has no ground and this is probably causing the short, so i removed it (left it loose) and tried to connect the batt. ground again. Still sparked a lot and i stopped. Only if i disconnect BOTH wires from the alt. can i connect the batt. ground successfully.

I would appreciate any help i can get as i don't have a car right now. Thanks.

[180fan]

is the plastic part on the back of the alternator still there by any chance? it's the only black piece of plastic that's attached to a post that you gotta put a ring connector on and tighten down with a nut. check for it.

[wadiad]

At first i left this piece on the old alternator as i didn't see any purpose for switching it to the new one. However someone pointed out to me (over the phone) that if the positive wire touches the alt. housing it will cause a short, and a light bulb went off - the positive (or i guess battery) cable connecter is a shape which protrudes toward the surface it's bolted to, and it was in fact touching the housing. I then realized the black piece you are asking about would separate it from the housing. Sure enough i installed that black plastic piece on the new alt. and it works! Now i just need a shorter belt and i'll be in business.

I appreciate your advice - thanks.