Take it from someone who has rebuilt 2 old AC filter motors (500 & 300) and 2 AC old power heads (402) now all working like new. The motor housing hold nothing more then a sealed electromagnet stator so there are no moving parts and the magnet is either working or its not. The dust you see inside the rotor housing (hole) and the noise you hear is the result of the rotor natural magnet vibrating on its metal shaft because the metal pin shaft and tiny hole inside the rotor (impeller and magnet) have worn each other out, why the dust why the noise. To check this you can compare the slop of the round impeller magnet on its shaft by wiggling it. A new magnet-impeller on its shaft will be tight with no wiggle room, while an old worn out magnet-impeller will be sloppy-seconds. If you buy a new motor housing, all you are buying is a new shaft because 9 times out of 10, there is nothing wrong with the motor-stator housing. Whether you save by buying a new shaft or buy the whole motor housing with a new shaft, make sure you buy a new impeller rotor magnet and impeller or the new parts will ware out on the old parts. Just like newlyweds you want both parts to be new so they can perform well overall, not mixed matched old/new where one is trying and the other runs out of gas.
