Battery light intermittently flickers on and off while driving on 2000 Volkswagen Jetta

Battery light flickers on and off occasionally while driving. Not on long enough for the alarm beep to sound. Installed a new (refurbished) alternator about a month ago, and battery is less than a year old. Frequency of flashing happening lessened once I turned off the A/C.

Asked by for the 2000 Volkswagen Jetta