I have a 1991 Janitrol furnace. The blower motor was replaced 2 years ago. The furnace works fine otherwise, flame comes on, the blower runs until the set temp, but after the blower shuts off, the motor is still humming, non-stop. Is the problem at the furnace or the house thermostat (the fan is set on "auto")

The motor or emf hum you are experiencing could be attributed to one of several items. First... if the blower motor has not been serviced since install, it's probably dirty and overheating. Second, if the capacitor is weak, it can make the motor hum. Third, the fan motor itself could be ready to fail... this is the least likely though. Call a reputable co and first have it thoroughly maintained then go from there. Ps... you should have preventative maintenance done every 6 months.

Are you sure it's a hum from the motor and not the transformer? If the blower motor will start back up by switchin the fan switch to on at the thermostat. Its not a motor over heating and may not be the motor at all.

True, transformers hum as well as do fan motors...