Troubleshooting auto electrical systems is the simplest thing, if you understand how electricity works. Electricity flows just like water through a hose. It starts at the battery's positive terminal, flows through the car's circuitry, then back to the battery's negative terminal. When problems occur, it's usually because the flow has been interrupted. A wiring diagram and multi-meter are the essential tools needed to troubleshoot. Once you know what components are in the system, you can use the process of elimination to determine what's wrong.