My furnace is having a disorder!! This is a gas Tempstar. The fan (blower) is staying on continuously, but the heat is kicking on, staying on anywhere from 4-9 seconds, then kicks back off for approx. 30-40 seconds before starting another round. At this rate, our house is staying around 65 and I AM COLD!! HELP!!

Dirty air filter? Defective fan switch? Defective high limit? Heat anticipator in stat not adjusted properly? It could be many items.

Clean flame sensor...