The EM-500-03 trainer allows instructors to demonstrate the operation of automotive charging systems controlled by a PCM. The synoptic diagram and the layout of all the control and instrumentation units provide clear and simple operation explanations to the user. The trainer is very reliable and equipped with all safety equipment required for demonstration. The EM-500-03 alternator trainer with a PCM controlled voltage regulator contains a variable speed drive that modulates alternator input (engine speed) as in an actual vehicle. The alternator has been modified to accommodate a load current of 25A in order to demonstrate the full load charging characteristic and allow the regulator to run at 100% capacity. This trainer can be used to help students understand the operation and common testing procedures of the charging system with PCM controlled regulation.