Relay help

I need some help understanding the concept of a relay. Why not splice additional wires instead? Can I mess up my trucks wiring system entirely by not connecting to the right pins on the relay? Can anyone please explain its functions more thoroughly?

 

A relay is basically a remote-control switch. It has 2 circuits inside - (a) the main switched circuit being activated / closed by the relay's action and (b) the actuator (that 'flips the switch' on the main circuit).

A relay allows you to use a low-power 'signal' to trigger activation of the main circuit. If the main circuit has a lot of power on it, the use of a relay reduces voltage load on your control circuits.

It's possible to damage a relay if the main circuit is relatively high-powered and you put the high power through the relay's trigger / activation circuit.

 

Is there a specific project you are working on?

A simple example would be wiring up fog lights. If you did not use a relay (30 amp in my project) you would then have all that current running directly through the switch on the dash. That would require a super heavy duty switch or you would run risk of burning the switch up.