Seems odd the alternator would/could function properly unless I race the engine, or run +/- 1900 RPM (about 60 mph), triggering the battery light to come on, as well as the voltage gauge to drop very low.
When mine was doing similar things it was bad "slip rings". I could easily see it when I pulled the regulator off the alternator. New alternator and no more problem. Cheers!
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