86 alternator question

[lukerman]

I bought an alternar from local store but it is missing something from the rear of alternator, which has one bolt holding it with one lead wire that plugs into back of alt. It is not the voltage regulator. Small black plastic square. Any idea what this is?

Thanks

i used the old black part on new alt and it is not charging. Not sure if alt is bad or this part is bad.

[JhwShark]

If you bought a part that is incomplete -- return it! Go somewhere else and get a proper alt...or if your like these guy's have them do the right thing...diodes maybe, a pic would always help.

[lukerman]

its the black square at the bottom of alt. about 6 oclock position

[JK McDonald]

Hey Lukerman - I believe the small black square item you are referring to is a capacitor used to smooth the output voltage of the alternator and help keep the rectifier noise out of the car's stereo/speakers. They are typically connected to the case (ground) of the alternator with a single silver lug and a short wire that connects to a positive source of the output voltage. They are fairly generic and can be an assortment of shapes or sizes.

You might talk to someone at an electrical shop that rebuilds automotive alternators and starters. They probably have lots pf these things just laying around. But I'd recommend that you just return the alternator if it's not charging after installation. A new alternator should be ready to go out of the box.

Good Luck, Michael