I have a Goodman Furnace 80+ installed by a HVAC Dealer. It's three years old. The problem I am having is when I set the thermostat back at night to 66 degrees and in the morning it sets up to 70 degrees the furnace runs for a short period (5 -10 minutes) then shuts down. Once the draft induced motor shuts down it immediately starts up again. This cycle continues until the furnace has satisfied the thermostat. I do not remember it doing this when first installed. Any explanation would be appreciated.