I have an original furnace in my house (probably 1963ish). It's a Furnaceman Model IG-125-3. It has worked fine until today. The fan won't turn off and is running continually. Is there a switch I can turn to make it stop?

I have an original furnace in my house (probably 1963ish). It's a Furnaceman Model IG-125-3. It has worked fine until today. The fan won't turn off and is running continually. Is there a switch I can turn to make it stop?

If you turn off the main switch you will not have any heat so I would not do that. Being the unit is pretty old I would think the fan and limit switch if so equipped needs to be replaced.