Car relays are essential components in modern vehicles, responsible for controlling the flow of electrical current to various systems such as the starter, headlights, and fuel pump. Over time, relays can malfunction, leading to issues such as failure to start the engine or non-functioning electrical accessories. Fortunately, testing a car relay with a multimeter is a relatively simple process, allowing you to diagnose whether the relay is functioning properly. In this guide, we’ll walk you through the steps of testing a car relay using a multimeter.
Understanding the Relay Before jumping into testing, it’s essential to understand the basic structure of a car relay. Most automotive relays have five pins: Pin 85 (Coil): One side of the relay coil. Pin 86 (Coil): The other side of the relay coil. Pin 30 (Common): The terminal that provides power input to the relay. Pin 87 (Normally Open): The terminal that delivers power to the output when the relay is activated. Pin 87a (Normally Closed): This pin provides power to the output when the relay is deactivated. Relays are designed to either close or open the connection between the common terminal (Pin 30) and the normally open terminal (Pin 87) when an electric current is applied to the coil. When activated, the relay switches, allowing current to flow from Pin 30 to Pin 87, powering the associated component. In its deactivated state, the relay connects Pin 30 to Pin 87a.
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