Ok so I traced it down to the connection at the blower motor. The connector must have been melted so the previous owner(s) instead of fixing the issue used RTV to make the plug stay in-place. Over time this must have worked loose or shrunk because of the cold weather. To temporarily fix it so I can have heat I jammed a sliver of wood between the plug and housing, jiggled the wire while it was on and fan stays on now. I will permanently fix it later this spring.