So I have a 99 Cummins and the driver side running light doesn’t come on but does for turn signal and hazards. On a possible related note my batteries die fast. I bought new ones and they were completely dead before a month and now I’m having the same issue two months later.

 

Dual filament bulbs. Try replacing it first.

Is your alternator charging your batteries? Or is there a draw that kills them quickly?

 

It only when a go a few days of not starting it

 

You may very well have a parasitic draw. You can likely find it with a DMM (or thermal imager). Just search YT for vids on locating a parasitic draw with a DMM