AROB

I have a Ruud 95% gas furnace, single speed. Its only about 3 years old. It has always cycled on and off before coming up to target temp. It will run about 10 mins, the gas shuts off and it continues to run to cool itself (or whatever). The instant the main blower shuts off the pre-blower starts up again and it relights and turns on and repeats...I tried replacing the thermostat batteries and made sure the filter is clean. I even tried running without the filter just in cast and it still happens. Any ideas on what to do in this case?