My alternator isn't charging my battery because of a bad connection with the pigtail wiring harness. I'm not able to find out if the harness is a short detachable one or if it's connected to the whole wiring harness for the entire car.

 

From what you describe, you should be able to repair any wiring or connection problem with pieces that are easily available at most auto supply stores. No need to replaceany harness.