Check to see if the belt from the jackshaft pulley to the crankshaft pulley is still there. BTW, just because the blower is turning at idle doesn't mean the lower belt is on. If the belt is still there, I would suspect it's something on the blower input/snout like a sheared blower pulley key, broken input shaft ect. Any of those thing would make a little noise, and that's why I think it might have broken a belt.
David