Car relays are integral components in automotive electrical systems. They act as switches that control high-power circuits using low-power signals. By understanding different car relay types, car owners and technicians can better diagnose and maintain vehicle systems, ensuring both safety and efficiency. In this article, we will explore the most common car relay types, their functions, and where they are used within a vehicle.

1. Standard SPST Relays (Single Pole, Single Throw) The most common and basic relay found in vehicles is the SPST (Single Pole Single Throw) relay. This type of relay features one input and one output, making it ideal for simple on/off functions. For example, SPST relays are often used in circuits that control headlights, horns, or wipers. When a small electrical signal is sent to the relay, it activates a larger current to power the specific device. This simplicity is what makes SPST relays so commonly used in automotive applications. 2. SPDT Relays (Single Pole, Double Throw) An SPDT (Single Pole Double Throw) relay is a step up from the SPST relay, providing the ability to switch between two outputs. With one input, the relay can choose between two different circuits. This type of relay is useful in situations where a component needs to perform two different functions based on conditions. For example, an SPDT relay might control a fan system in a car, where it switches between low and high speeds based on the engine’s temperature.