What does a relay switch do in a 1970 truck?

A relay switch in a 1970 truck serves as an electrically controlled switch that allows a low-current signal to control a higher-current circuit. This is particularly useful for powering components like headlights, fuel pumps, or starter motors without overloading the vehicle's wiring. By using a relay, the truck can operate these high-draw devices safely and efficiently, reducing the risk of overheating and electrical failure.