What is the "capacitor" in my furnace, and what does it do?
A bad capacitor can cause damage over time to a furnace''s blower motor. Only let it run just long enough to hear the hum. If it doesn''t start, turn the thermostat back down or cut the power to your furnace. Letting it run longer could make the problem worse and do more damage to the furnace, resulting in a much higher repair bill. ...