because of its age could be anything. the old blower could have blown fuse. I believe there is a fuse just for the blower motor. use a meter check for volts. a wiring diagram would help with this . if you have no luck on finding the loss of volts the resistor assy you could install a fused wire like 20amp and feed the blower resistor assy .then you will have the blower working .. that will give you more time to find the loss of power to blower.