Rev Up and Rule the Road 2025: JJ Keller Entry Level CDL Driver Test Challenge!

A voltmeter is an instrument specifically designed to measure the electrical potential difference, or voltage, within a circuit or system. In a vehicle, the voltmeter provides vital information about the electrical system's health, particularly the battery and charging system.

When the voltmeter registers the voltage, it allows a driver or technician to assess whether the electrical system is functioning properly. A healthy battery typically shows a voltage reading between 12.6 to 12.8 volts when fully charged and the engine off. Under load, with the engine running, it should generally measure between 13.7 to 14.7 volts, indicating that the alternator is charging the battery effectively.

This measurement is crucial for ensuring that other electrical components, such as lights, radio, and ignition systems, are receiving adequate power. Being aware of the voltage levels can help identify potential issues before they lead to breakdowns or failures in the vehicle’s electrical systems.