I was cleaning out the back of my Norcold refrigerator yesterday and decided to take off the cover to the bottom of the flue. What I saw was a huge pile of fine rust flakes in the sheet metal tray under the burner. I cleaned it all out and tried rapping on the side of the flue, but wasn't able to get any more to fall out. Is my refer on it's last legs? I assume it's the original that came with '92 motor home. It still works OK, both on propane and AC, anything I can do to stop the deterioration?