Sunline has tended to use the same external plastic fixtures (door window framing, range hood vent flap, refrigerator vent grilles, etc.) as most other manufacturers. And the result is usually the same....after 2 or 3 years they yellow, and after 5 years they tend to crack or otherwise deteriorate....the result of ultraviolet radiation in sunlight (and the cheap plastic used).
A fairly quick, easy, and inexpensive solution to the problem (if you haven't waited until the fixture is crumbling) is as follows.........
(1) Clean with Fantastic, 409, or other cleaner, and then carefully wipe the fixture down with a "sanding prep".
(2) While you're waiting 15 minutes for the sanding prep to evaporate or dry, carefully mask the area around the fixture (you're going to spraypaint).
(3) Using either regular K-Mart Dutch Boy (or any of the new spray paints specifically made to cover plastic) in Satin White
, spray the fixture (2 light coats, at least 12 minutes apart). Be sure to wait at least 15 minutes before removing the masking tape.
You'll find this process covers existing yellowing, and prevents future yellowing or deterioration for 4-6 years....and then you can redo it again.