79 280SL Alternator problems
 

My battery light recently came on. I have checked and charged the battery looking for tips on how to test the alternator? I have noticed that when i increase the RPMs the battery indicator fades.

Check your voltage regulator....
 

If your voltage regulator can be changed independently of the alternator, I would check that out. You may be wearing the carbon bushings on the reg to the degree where idle speed no longer provides a charge, either way, it will soon go altogether.

Worth a check, voltage regs are the cause of a majority of MB charging issues, and generally cost $10 bucks at your local parts shop.