It depends on the motors you're using. If it's the VMK19 from Kleen-Rite, I don't waste any bother changing the brushes if they're worn all the way down because they never last long once they've worn that far. The commutator always gets damaged and there's no fix for that.I’ve J.E. Adams super vacs that have 3 motors each. On one of my vacs 2 of the 3 motors are not working. What’s the easiest way to determine my problem? Could it be brushes? Is it a failed motor? How do I tell?