Do lights flicker? (doesn't really matter though)
Could be the voltage regulator not allow alternator to properly charge battery. But I assume you have internal regulator in alt so maybe not.
You can go to Auto Zone and they should be able to give you a FREE electrical systems diagnostic (includes alt, battery, volt. regulator).
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351W-powered 1979 Ford Mustang notchback
Stock 5.8L under 4" cowl, C4 w/ shift kit
Holley 750 cfm, Edelbrock Performer RPM intake
1 5/8" MAC shorty headers, Al driveshaft
2.5" Off road H-pipe, 2-chamber Flowmasters
Front: 225/60/15, Rear: 255/60/15 Eagle GT II
Weld wheels (15x6;15x8), 8.8" Rear w/ 3.55s
14 x 4” K&N air filter (getting the Xtreme setup someday)
"Red, thou art my companion. Hasten now your quickened metamorphosis to Green that I may conquer all who dare abide there beside me. May they be left thither behind burnt black." ---Fox Body