Hey guys I was wondering what the point of a relay really is? Now I don;t have a computer in my car anymore so the fuel pump is hotwired with 12v key on the the green wire out of the relay. But if theres a fuse for the fuel pump over by the battery then what purpose does this relay serve? I always thought a relay was kind of like a fuse but I think I am way off. thanks for an info guys. Also I would liek to replace my fusible links with inline fuses, Now how would I know what amp fuse to run?? thanks

 

Most switch and sensor contacts are designed to only handle a relatively small amount of current because they have to be small enough that only a small amount of mechanical force is required to operate them. Running too much current through them can cause the switch to fail or burn up. A relay is like a switch, except that it's operated by an electromagnet. The electromagnet requires only a small amount of current to operate, but it can operate a much larger switch which can handle more current. The same thing applies to computer controls, the ECM could never directly switch the 40 Amps that the fan draws, so a relay is used.

There's a reason fusible links are used instead of fuses. A fusible link can handle a lot more current than a fusible link. You're better off leaving them alone.

 

heres everything you ever wanted to know about relays:

http://electronics.howstuffworks.com/relay.htm



the point of a relay in your case for the fuel pump in short:

the fuel pump draws alot of power.
if you wired the fuel pump thru the ignition switch, it would pull too much power thru the ignition switch and burn it up.

instead, the igntion switch powers the relay. the relay, using thicker wires for less current loss, connects the fuel pump directly to the battery and gives it full power