pull inducer fan motor off, pull assembly to see botom of heat exchanger and you will several tubes (anywhere from 10 to 30 tubes) will have a piece of metal in them pull meatal out and clean. take a shop vac and suck out the tubes, that should take care of the problem if it is a stopped up heat exchanger. warrenty most likely is only on the heat exchanger. i don't feel you have an ignition problem. still feel that it is a stopped up heat exchanger, so be perpared to get dirty.