Recalibration is a simple step that you can perform on your sander if you should notice that it seems a little wobbly or off in its performance. This typically occurs if you do not use the power switch to turn off your sander before unplugging it.
First, make sure your sander is unplugged. Hold down the minus button for about 5 seconds and plug the sander in. You will hear a series of 3 audible beeps. When you do, release the minus button, and press down on the paddle on/off switch. Next, press the on button and run through your different speeds to check that it sounds correct at each speed.