I have a c/a system. My furnace is heated by oil. My thermostats are set to heat. When the furnace kicks on hot air comes up. Once it gets to the temp furnace kicks off but I get cool air flowing. I have two zone heat and when I turn up the heat upstairs I get that smell as if it's the first time my heat has been on?? I just don't undertand why cool air is coming up threw the vents? Help!
