The plasic cowling and trim of my ceiling vent fan broke out with an ugly brown "rash" two years from date of manufacture (2007). Assuming that it was rust over metal (silly me) I pulled the offending parts (had to cut 4 wires) and took the offending parts to my shop for re-painting. When I discovered I was dealing with plastic, I turned to 320 grit sandpaper. I eventually removed the brown stuff to a satisfactory level. The offending gunk seems to be a clear overspray applied during manufacture that discolored after 2 years.
Has anyone else out there run into a similar situation and is there an easier way to treat the situation?