I HAVE A cOMFORTMaker rpj11 furnace. I foolishly had the flame sensor replaced by a contractor who said that was what was causing it to turn the burners on for a few seconds and then turning off. It did not always turn off at a consistent time frame . He charged me what I consider an exorbitant fee because the problem still exists. He said my pressure switch had mositure in it and so he blew into it. He now says I need a new motor and pressure switch. He suggested that maybe one of my return vents ad blockage . Any suggestions?

Yea get your money back and call a real professional.