I have an old furnace from what appears to be the 70's. The blower motor quit working. The motor was simply humming and very warm so I changed the motor out with a US Motors brand motor. The wiring schematic on the motor was less than stellar. In lieu of stating hot/black wire etc it said "ungrounded line". I took that to mean hot wire and hooked it up accordingly. The new motor is doing the same thing (Simply humming.) Any ideas? It's 48 degrees in my house!