178 Auto Electricity and Electronics Copyright by Goodheart-Willcox Co., Inc. Some older meters are not auto ranging and must be switched to the correct range. For example, the meter might have a kilohms setting, which means each reading must be multiplied by 100 to fi nd the value in ohms. If the reading is in megaohms, you must multiply the reading by 100,000. Various voltage and current settings are also provided on some meters that are not auto ranging. Voltage Measurements Voltage measurements are also useful in determining the condition of a circuit or components. By checking the voltage, you can gather more information about the electri- cal problem. For example, by measuring battery voltage, you can check the charge or condition of a vehicle’s battery. A fully charged 12-volt battery should have 12.6 volts. If your voltmeter only reads 11 volts, the battery either needs to be recharged, or it has an internal problem, such as low electro- lyte, deteriorated plates, or shorts in cells. As another example, imagine that an engine will not start and there is no spark at the plug wires. You might mea- sure the voltage supplied to the ignition coil. If the voltage is low going to the coil, it may not be able to produce a good spark. Your tests might tell you that a high resistance or shunt to another conductor is preventing normal voltage supply to the ignition coil. Th is will be discussed in detail later. Figure 9-21. Press the Zero button while touching the two leads together to recalibrate the meter to zero before taking resistance readings. (Fluke) Press to Recalibrate For Resistance Readings Figure 9-22. Making ammeter readings on a digital multimeter. A—Turn the function knob to A for amps. B—Plug the test leads into the correct sockets for ammeter use. C—Notice the prefix in the units display. What does this ammeter read? (Fluke) C B A Figure 9-23. The bar graph on a digital-analog multimeter allows you to see fluctuating values easily. In A, the analog bar graph shows almost zero resistance. In B, it has moved all the way to the right to show a maximum resistance reading. This can happen very rapidly and in quick succession, showing rapid fluctuations clearly. (Fluke) B A