Hey, I have a question. If you connect the speed controller without anything connected to it, does the potentiometer work? Mine doesn't change the voltage until I plug something in and I don't know if my unit is faulty.
When you plug the voltage regulator into a wall outlet and turn it on, it will display (or should display) the voltage that is coming from the wall outlet into the regulator. When you plug a motor etc. into the voltage regulator, then it will show the voltage that is going to the voltage regulator's outlet (depending on where the dial is set). The display will show approximately 0 volts when a motor etc. has been plugged into the regulator (if the potentiometer is rotated completely counter-clockwise), but when you start to turn the potentiometer clockwise, the display will probably not show voltage on the display (from 0), until there is enough power available at the voltage regulators outlet for the motor to start running, as that is because of the size of the potentiometer inside the regulator. For the regulator to supply enough power to start the motor, you may have to turn the dial half way or more, and that is (I believe) because the potentiometers in these devices are (for the consumers' intended purposes) too big in ohms rating. In the case where the potentiometer has to be turned half way or more to start a motor, you would need to replace the potentiometer inside the voltage regulator with a smaller one. I tried to make this explanation as short as possible, but there are a lot of complicated things going on inside there LOL... So to answer your question in short - No, there is nothing wrong with your voltage regulator. I think I may purchase one of these and create a video about how they work, and also how to upgrade them to make the dial work sooner (if needed)...