My ICP Comfortmaker furnace is well maintained (even the blower bearings are oiled!!), and I am extremely happy with its dependability, but every couple of years, it develops a false start problem, and its always the same reason -- the flame sense rod has finally become dirty. A quick cleaning with fine steel wool, and everything's great again. I do have some curiosity-type questions however:
1. What exactly is the material building up on the rod? Is it just normal byproducts of combustion of natural gas? Or is it an indicator of some type of impurity in the gas/air?
2. Is the flame sense rod solid all the way through, or is it plated with some special metal (and will I eventually wear through that metallic plating?)