Y'all were so helpful to me once before since buying my 18-year-old daughter's 1990 190E, I'm going to throw you another one! My daughter's headlights are "pulsing"---the intensity of the beams dims and brightens in a rhythmic manner, almost like they are pulsing. Not fast enough to be flickering, really, but about every couple of seconds. What could be causing this? And if you have a good idea of what it is, what is the most economical way to go about fixing it? []