Hello there this is my first post on this forum so i apologize if I'm doing this wrong but,

My car is a 2003 Chevrolet Monte Carlo SS 3.8 V6. I just got new OEM headlights for my car because the everything on the drivers side was out. Now only my passenger side high beams turn on and i can't seem to figure out what is causing this. I've replaced both fuses for both headlights and tried changing the bulb for another one that i know works but still nothing.

 

And it started after changing the headlights? If so, that is really odd. Since you swapped bulbs and the problem persists, my guess is either a damaged wire or the multi-function switch (aka the turn signal stalk). To figure it out, you will probably need some wiring diagrams and start tracing things out.

 

Try checking the spring contacts at the base of the socket. They might not be making contact with the bulb.