In the EnerJeeps unit, students design, build, troubleshoot, and test electric cars, constructed from everyday materials. First they connect a motor to a battery and learn how to reverse it. They construct switches to turn the motors on and off. Then they figure out how to use the motion of the drive shaft to move a homemade car, either through direct drive, friction drive, propeller drive or belt drive. They learn troubleshooting techniques, which allow them to identify sources of friction or to isolate a bad electrical connection. Students add circuits for lights and a horn. Finally they write instruction manuals for making their cars and troubleshooting guides, then present their cars in an Auto Show.