Short heat cycle and furnace won't shut off
I have a Luxaire Deluxe High efficiency furnace model 3 PBNU LD12N080B. We bought the house 2 years ago and all has been fine. We noticed just recently that the blower seams to be running all of the time but the furnace only comes on for a short time and never gets up to what is set on the thermostat before shutting back down, but the furnace continues to hum, not the blower motor. When it does come on it does blow good hot air. I do not have a manual for this furnace and was not able to find one on line.
