Furnace fan is 12V and should only run when the furnace is running and for a short time after the fire in the furnace is shut off. 120V outlets are usually controlled through circuit breakers. Possible that your wiring may have been a hungry mouse snack. Troubleshooting using both a multimeter and an inductive voltage sensor seems to be in the future.
Bill & Anne + FBs Athena, Jada & Cupcake
Wilson III: 2015 Ram 2500 6.4L Gas 4x4 4.10 CC SRW
Gypsy II: 2013 Kodiak 279RBSL with table & chairs instead of a dinette