The 25+ - Why does everything need a relay?

 Why does everything need a relay these days? Years ago we didn’t use any.

That’s right...almost. Relays were seldom used before about the mid ‘70’s except for two specific circuits.

Many of you will remember horn relays. They were a rectangular box that attached to the firewall (and frequently gave us trouble). Also, a starter solenoid like the ones that mounted on the inner fender liner were actually a relay - the word “relay” describes their function while the word “solenoid” describes how they did it, which was by using a coiled magnetic wire to create movement when energized. There a few reasons that relays are used much more today. 

The first reason is that relays have gotten much better, smaller and less expensive. In the past, an oversized switch would preclude the need for a relay, but that big switch might be expensive and heavy. In today’s world, a small switch, maybe even a micro-switch or touch pad switch, can trigger a small, light, inexpensive relay for less money and weight than that big switch. Even the size and weight of the copper wire can be reduced if the relay can be placed fairly close to the load. A second reason is styling, which has pushed for smaller switches that need a relay to do the job as far as amperage carrying capability.

Third, we are demanding more of our electrical systems - more features, more devices, and more amperage - all of which lead toward more relays. Even our old tried-and-true circuits like head lights need more amperage power to feed higher wattage bulbs like the halogens and High Intensity Discharge (HID) lights. But don’t fret, relays are our friends. We just need to understand them and use them for their advantage in specific circuits.

Steve Watson, Watson's StreetWorks, http://www.watsons-streetworks.com