350 Automatic Transmissions and Transaxles Copyright by Goodheart-Willcox Co., Inc. Test Equipment To test electronic components, you will need some or all of the following testers. This test equipment was dis- cussed in Chapter 2 and will be briefly reviewed here. Scan tools were discussed previously. Voltmeters can be connected to read the voltage available at an electrical connection. The voltmeter in Figure 14-14 is being used to measure voltage at a wire connector. The positive lead is placed on one of the connec- tor terminals, and the negative lead is connected to a good ground. In Figure 14-15, the voltmeter is reading the volt- age across a connection as current flows through it. If the connection has excessive resistance, current will try to flow through the meter, creating a voltage reading. The connec- tion must be cleaned or replaced if the voltage is higher than the maximum specified. Figure 14-13. Scan tools can be set to display engine operating conditions in numbers or graphs. A—Scan tool displaying oper- ating conditions in text form. B—Scan tool displaying graphs of operating conditions. A B Ammeters can measure amperage flows up to 10 amps. More amperage will damage the ammeter, so most modern ammeters are equipped with an inductive pickup, Figure 14-16. This pickup is clamped over the current- carrying wire. The pickup reads the magnetic field created by current flowing through the wire and converts it to an amperage reading. Figure 14-14. Using a multimeter to measure voltage at a fuse box connection. The negative lead is clipped to a ground con- nection and the positive probe is touched to the positive con- nection. The multimeter is set to read DC voltage. Figure 14-15. Checking the voltage drop across a connector. More than a small voltage drop indicates a high-resistance connection. Actual maximum voltage drop varies from one cir- cuit to another and depends on the amount of current flowing in the circuit. (General Motors) V