I drive a 2014 Silverado 1500 WT, and recently noticed my low beam headlights have stopped working. I still have daytime running lights and high beams. I also noticed a humming, like an electric motor/fan running, after I parked and turned off the ignition. I don't think I've heard that noise before, but I don't often sit in my truck after parking it. Knowing I've had issues with my headlights lately, I turned off automatic light control, and the humming stopped. Any ideas?