1. Check battery:

. Check the battery voltage, Turn off the engine, voltage 12.6 he must have.
. If battery voltage is low, So the battery is charge or it replace.

2. Inspect the alternator belt:

. Turn off the engine inspect the alternator belt, If belt worn out, Loss, Or broken, So replace it.
. Ensure the belt, If it slips, Don’t do it.

3. Check the alternator and connection:

. Check the alternator wiring.
. Ensure the battery terminal and alternator connection is correct.

4. Test the alternator output.

. Check the alternator output voltage use the multimeter, Turn on the engine connect to multimeter in the battery terminals.
. Output the alternator 13.6v from 14.8v should be between, If voltage is low, So alternator repair or replace must do.

5. Replace the alternator.