How Does A Relay Work?
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From: Ft. Lauderdale, Fl.
How Does A Relay Work? How does a relay function? There are four & sometimes five terminals on a relay. Can someone tell me each terminals use? When should a relay be used? Thanks, Gar
Relays are for when you need to switch a large amount of current - something most switches (including PCM's ) don't do well, or for a few other reasons.
Relays have a little soleniod type switch - two of the connectors are for the input (smaller wire that goes from a switch or from the computer) - one hot and one ground.
The other 2 or 3 poles are for what you are switching, and often larger wires - generally powered wires. One would be for 12v in, the other two are for 12v out. One of the outs is for a NC - normally closed setting and the other is for a NO - normally open setting. NC - lets the 12v pass though the relay with no signal from the switch, and cuts power when the signal from the switch is on. NO - means no power through the relay until the relay gets a signal from the switch or computer.
Hope this helps.
Relays have a little soleniod type switch - two of the connectors are for the input (smaller wire that goes from a switch or from the computer) - one hot and one ground.
The other 2 or 3 poles are for what you are switching, and often larger wires - generally powered wires. One would be for 12v in, the other two are for 12v out. One of the outs is for a NC - normally closed setting and the other is for a NO - normally open setting. NC - lets the 12v pass though the relay with no signal from the switch, and cuts power when the signal from the switch is on. NO - means no power through the relay until the relay gets a signal from the switch or computer.
Hope this helps.
go here www.madelectrical.com
there is plenty of info on how relays work and how they can improve old rides
there is plenty of info on how relays work and how they can improve old rides
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Relay Function Info... Thanks James & Schitzo, great info. This helps alot. If a 30 amp relay is used, should the fuse size, in front of it, also be a 30 amp? 20 with a 20, and so on? 
Thanks
Thanks 
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From: Tampa, FL
The fuse would depend more on the device being powered, but not more than what the relay can hold. You would want no more fuse than the amperage rating for the Relay, so you could use a 30 amp relay with a 20 amp fused circuit, but not vice versa.
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From: Downers Grove, IL
Originally Posted by BLWN1
Do I need them with a standalone setup, or will they come with the harness?
