I had a 3/4 ton pickup that had that happen - it turned out the turn signal stick had to be replaced. It controlled the dimmer on the headlights also. That would be an easy test to determine if the same problem. Good luck.
Stan & Dorrie LeRoy, always seeking lighthouses in our 2008 Windsport 36R
Smart Car toad on trailer
2 Spoiled Shitzus