A true AC motor will not work with a rheostat controller. Those motors that are called AC/DC will work. The AC/DC motors have brushes, a true AC motors do not use brushes .....Brushless motors are constructed in a reverse fashion from the traditional form. The rotor contains a permanent magnet and the stator has the conducting coil of wire. By the elimination of brushes, these motors offer reduced maintainance, no spark hazard, and better speed control. A universal motor, an AC motor with carbon brushes and a commutator, can easily be controlled with a rheostat or electronic voltage control. A 2-speed motor is unlikely to be a universal motor.