G-R-O-U-N-D-S, you would be surprised it could be a ground not even close to the alt. causing the problem.
It could also be that when the old alt. went bad, it weakened the battery, when he installed the new alt, it failed to initulize the new alt causing it to go bad. Take the alt. off and have it bench tested. "Most places will do this for free".
Finally check/test all the little boxes on the driver side fender. On might have gone bad.
