When I have the lights set to "auto" they are always on now, even in bright sunlight. This was not the case for the first 6 months or so when I bought the car; they were truly automatic, based on daylight or cloudiness, etc. I washed the car (in a general manner) but don't know where the sensor is to give it a better scrubbing. It's not something I want to bring to the dealer for if I can just check to see if there's road grime built up, etc. The car is 9 months old with 10,000 miles.