How Does A Relay Switch Work In A Car

Whenever you operate a switch to an accessory in your car that carries a lot of current such as the lights wipers or horn you run a small amount of current through a relay which in turn closes contacts to operate the accessory.

How does a relay switch work in a car. Firstly using a relay means the switching circuit does not require a high current rated switch or cable which reduces cost and weight. A changeover relay is built with two circuits instead of one and five pins rather than four. Relays in general are used to enable a low amperage circuit to switch on or off a higher amperage circuit like turning on your headlights. If a component that is fed with electricity through a relay see how car electrical systems work terminal of the battery to the feed terminal on the component thereby bypassing the relay and supply wiring.

If one of your accessories doesn t come on and you suspect the relay is bad you can perform a few simple tests. Typically the relay is switched manually using push or toggle switch an everyday example of this is the car ignition switch used to start the engine. There are several benefits of using a relay in a car. If it works then the supply is faulty and the fault will be in the relay or the connections to it.

Automotive relays of all shapes and sizes can be found in just about every car truck and even boats. Record the measured voltage and if it is not the right amount then your relay switch is working poorly. By putting an end of an alligator clip to a grounded spot you will then touch a wire of the relay switch with a multimeter. Remove your car s dashboard as this is the main site of the relay switches and then turn your car on.

Here are two simple animations illustrating how relays use one circuit to switch on a second circuit.