I don't have a wiring schematic. But in the furnace, there has to be a thermo switch somewhere that keeps the blower going after the thermostat on the wall turns the burner off. The blower has to cool the furnace plenum down once the burner shuts off. Once the plenum cools down, the thermo switch opens and turns the blower off. It sounds to me like maybe that thermo switch is stuck, keeping the blower on all the time.
FAA A&P mechanic, ex-RV dealer parts dept
Retired B-52 Gunner/Flight Examiner, B-52 Crew Chief
2016 Jayco Eagle HT 29.5 FBDS w/ 15,000 BTU AC, 50 amp service, upgraded counter top, thermal pane windows, elec. stab jacks, outside grill, backup camera and MORryde pin box.
2011 GMC 2500HD DURAMAX/ ALLISON