In automotive systems, what does a relay typically control?

A relay is an electromechanical switch used in automotive systems to control a circuit by a low-power signal or to control several circuits with one signal. The primary purpose of a relay is to manage high-amperage loads—such as motors, lights, or other electrical components—that require more current than a standard switch can handle.

By using a low-amperage signal, such as that from a switch inside the vehicle, the relay can engage a much larger load without putting strain on the control circuit. This allows for the safe operation of high-power devices while ensuring the control device remains safeguarded from the high current that those devices would draw. Therefore, the relationship between low-amperage signals and high-amperage loads is fundamental to the function of relays in automotive applications.

The other options do not encapsulate the primary function of a relay. For example, total engine power, engine temperature, and battery discharge are influenced by various components and systems within the vehicle but are not directly controlled by a relay in the same manner that high-amperage loads are.