Final answer:
The equipment that cannot be used to perform a charging system test is A) dwell-tach, which is typically used for measuring dwell angle and RPM, not for charging systems. Load testers, scope tools, and VOMs are appropriate for such diagnostics and provide various measurements necessary for assessing the charging system's health.
Step-by-step explanation:
The subject of the question involves the equipment used to perform a charging system test on a vehicle. Among the options given, A) dwell-tach, B) load tester, C) scope tool, and D) common VOM, the one that cannot be generally used for a charging system test is A) dwell-tach. A dwell-tach is typically used for measuring the dwell angle and engine RPM, not for evaluating the charging system as a whole. A load tester is used to assess the battery condition under load by measuring terminal voltage, as exemplified in Figure 21.13, where a large device with a small resistance dissipates a significant amount of power. A scope tool or oscilloscope can be used to observe the detailed waveform of the charging system, helping diagnose issues such as ripple voltage. Lastly, a common VOM (Volt-Ohm-Milliammeter) can be utilized for measuring voltage, resistance, and current, which are pertinent to troubleshooting a charging system.