If you are having issues with the Bosch PS21, try referring to the Bosch PS21 Troubleshooting.
Background and Identification
The Bosch PS21-2A 12 volt max two-speed pocket driver introduces a torque range of 0-350 rpm and high speeds up to 1300 rpms. Weighing only 1.8 lbs, it has the best torque to size ratio in its class and can produce 265 In.-lbs of torque. With a Lithium Ion battery, it can last hours depending on the use and has 20+1 clutch settings to enable precise user controls. With an integrated LED light, it can be used to illuminate the workspace and allow for optimum usage. The identification number for this model is PS21 3601J92911.