the rear PTO turns but the fan doesn't move. I can turn the fan by hand. Is there a shear pin in there somewhere? If so, where? I don't have the owners manual.
I had a bagger on my BX23, I am not sure if it is the same as yours but it broke the pin twice. If you take the plate off of the assembly to expose the shaft that drives the fan you will find a crazy shoulder bolt on there that acts like a shear pin connecting one shaft slipped inside of another. I have about 15 of these bolts but don't need them any more because I traded for my B3030, if you lived close it could have been a score.
Yes there is a pin, look by the PTO shaft. I had one and if I remember correctly its a pin on the blower between the coupler and shaft (not PTO shaft) but the blower shaft the runs through the coupler, kinda bolts them together and shears if you hit something too big and it gets to the blower fan.