PB100 Electrical System Circuit Tester Functions: 1. Perform these functions: power injection, measuring, ground testing, polarity checking, continuity testing and component activation. 2. Read the AVO meter, voltage, current, and resistance easily. 3. Press the power switch lightly and get the instant heat ground lead to energize the electrical components, such as the cooling fan, relay etc. 4. Activate the components by using the hot wire and ground lead simultaneously. 5. Determine the positive, negative and open circuit quickly. 6. Test the bad ground contacts quickly, follow and locate short circuits without wasting the fuse. 7. Test the continuity of the power switch, relay and diode quickly. 8. Protect the tool from overload through the inner circuit breaker. .