If the fuses are good, then check the light switch itself. It could be that over time the current draw on the light circuit has damaged the plug-in connection at the switch. check the fuses
It isn't getting voltage or ground
You probably have a rusted or disconnected ground wire to the running lights and side markers.
It is built in to the alternator.
yes
Defective voltage regulator. It may be built into the alternator.
Rr t/lps its a 10a fuse
No.
headlights
Sounds like the charging system is not working properly, if at all.
NO , Not from the factory.
Yes
I have a 1999 chevy Silverado how to fix my day time running lights