I have a 99 chevy tahoe 2wd. I turn my headlights on and ONLY have parking and markers. Flipped the high beams and nothing I drove anyway and as soon as accelerated the low beams and high beams came on. Worked all tge way to gas station. Shut it off got back in after getting gas and tge same no lights! HELP PLEASE. I think its a headlight switch on dash. But idk

 

I'd start with checking the voltage across the battery terminals with engine running at idle, and also to get the battery tested UNDER LOAD.

 

I did, but did not post results. I later traced a ground problem back to headlight switch. If you messed with the dimmer switch with headlights on the lights would come off and on. I replaced headlight switch on dash and fixed the issue.