on my alternator the bolt for the wire that goes from to the back of the alt to the battery is loose and turns when i try to take the bolt off. So there was alittle plastic piece i took out between the alt and bolt. Now when the bolt with the wire touches the back of the alt it makes a spark..

why does it do this?

 

alternator is grounded to the engine. that plastic piece is to keep that from happening. if you are having problems with the bolt turning when you are trying to take off the nut, take another small wrench or plyers and hold the inner nut, while you pull off the outer.

 

the plastic was an insolator, kept the bolt from grounding out on the alt