RobertYou

so I have a Mercedes 2010 C200 which I need some help with. My Daytime running light was playing up for a little bit, initially I thought I needed to replace it but then one night i came home and I turned my car off, took the keys out of the ignition and i realised after a few moments when all the other lights of the car turned off that my right daytime running light was still remaining on... like i said when everything was off. I've taken it to several mechanics, even a Mercedes specialist and they find it weird and can't Seem to find out what has happened to it. is there maybe a switch that I haven't accidentally hit which keys the right daytime running light on after the key is out for safety reasons. could someone please help me and explain why this is happening?