Problem: This Altima originally came into
the shop because the battery light was ON. The technician
diagnosed the problem as a bad alternator and replaced it. When
he started the engine to test the charging system, the new
alternator quickly became very hot. He replaced the alternator
again assuming the first one was defective. The second alternator
did the same thing (A hand-held digital temperature sensor read
Details: A call to ALLDATA Tech-Assist
provided some good insight. The consultant advised the tech that
is was possible that one alternator could have been bad but the
same overheating problem with two alternators was not likely. He
suggested checking the resistance between the alternator
housing/case and the negative battery post. If it was high, the
tech needed to check the engine ground cables.
The technician found that there was high resistance to ground at
the alternator case. A closer inspection revealed a corroded
ground cable on the engine block.
Confirmed Repair: The tech cleaned and
reinstalled the engine ground cable. After that repair, the
resistance to ground at the alternator was acceptable and the
alternator no longer ran hot. Cleaning the ground cable resolved
the problem. Fixed!