I live in an older mobile home and have a coleman presidential II furnace. When I turn it on, the pilot is lit and it produces heat, but the blower is very loud like banging. The impeller (?) the round thing that spins seems to be hitting the sides. There is nothing holding it to the shaft. The air is not blowing through the vents. Am I missing a piece to hold it together? Would this cause the heat to not be forced through my vents? How do I fix this?