I had an alternator one time that appeared to work fine. Show charging on the amp meeter, no light. But after driving around for a while at night the car would not start. Turned out to be an internal short in the rotor.
My mothers town car ran fine and did not have a gen light, but once shut off for several hours, the battery was totally dead. A diode was shorted.
So yes, it is possible for the system to look fine but not be.
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