I had the same thing happen on mine after an accident. The accident caused a very small crack on the back of the housing that I didn't notice in time to seal it. Anyway.... this allowed moisture on the inside of the light and within a month... the whole upper part of the headlight had turned yellow. I noticed the crack when I did my DIY black housing headlights. I tried using a very fine sand paper (2000 grit) to remove the yellow film on the inside of the clear cover but that didn't work. Maybe a buffer with rubbing compound would have worked but it would have been really hard to reach in there with a buffer. In the end.. I had a friend who had a headlamp with a broken housing so I replaced the clear cover on mine with his.