| Automotive Relays - Garage - Universal Tech
If you work on cars you’ve probably heard of relays; in fact, we often cover using relays in our tech articles. Following detailed instructions to wire one can work, but understanding what makes them tick allows you to take full advantage of these amazing little creatures. While there are many uses for relays, the most common is for switching a device such as a cooling fan, fuel pump, horn, nitrous solenoid… almost anything that draws high amperage. The reason is simple; relays allow us to control an accessory that draws a lot of juice through a light-duty remote switch or switching device. This basic use of relays is what we will focus on throughout this article. Just think of a relay as heavy-duty electromechanical switch, made up of an electromagnet and a set of contact points. Still a little confused? Don’t worry; we’ll break this down further as we dissect one of these little buggers to show you its internal functions.
| 01 Looking at the base of most relays, you will find between four and five terminals, each with a corresponding number. For a basic switching application, only the outer four terminals need to be used. For this article, just think of the terminal in the center as a middle child and ignore it.
| 06 This is a close-up of the contact points. These contact points make up the switch portion of the relay. Think of this as a heavy-duty switch capable of handling 30 to 40 amps (depending on the rating of your relay). To help put this into perspective, a typical automotive fuel pump or radiator cooling fan draws 15 to 20 amps).
