My chevy pick up battery went dead I replace for a brand new but the battery was not charging by the alternator so I pulled the alternator and I went to the shop to see if is was working and it was working good. The problem was that the alternator was not charging so What I did that night I put A cable from the alternator directly to the battery to see if it works Yes It works
My Question is If it could be a fuse a relay from the original cable to the battery Can Any one tell me how to repair this issue.

There may be corrosion at the battery cable, particularly POS cable. Many time the corrosion will be hidden inside the battery's cable but can be detected by close visual inspection of the cable. Look for evidence where the cable contacts the battery post, where the battery bolt contacts the cable, and check the cable itself for internal corrision by looking for bulging and swelling cause by build up.

Good luck.

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Does that have a Built in Regulator, or external regulator? What year, type of Truck?