I was hoping it was just a switch, it seems to cycle the blower fan more and more. I have a parts furnace and I switched out the round two pronged switch that was labeled "fan" and it seems to just changed the time in between the cycles

I have a Colemen model #8866b701 the heating cycle runs fine after the house is up to temp and it shuts down like it should the blower motor will start and run for 30 secs to a min, this will happens three or four times. What should I test or look for? Thanks for any help.