There are 4 limit switches in series and I think they are working as they should. Could it be because I have all the basement heat vents blocked off? The rest of the house (2 floors) are all open. I don't have a need to heat the basement. Also, how hot should the exhaust duct get? Mine gets too hot to touch which makes me think there could be some obstruction in it on the roof (birds nest maybe). Thanks!