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[quote="KikiTheCat"]by the way, if relays seem confusing just keep this in mind.
a relay is basically just a junction for two circuits. one circuit is low current (the trigger) and the other circuit is your high current circuit (devices, etc driven from the battery/alternator)

when the low curent line gets voltage, it closes a switch in the relay to complete the second circuit, allowing whatever you're using the relay for to have it's 12 volt power delivered directly from the car's electrical system for more current, instead of being fed through the trigger circuit, like a head unit's REM wire, which can only supply around 250mA of current as opposed to the heavier wire from the battery that can supply several amperes.[/quote]
thanks that made it clear

by the way, if relays seem confusing just keep this in mind.
a relay is basically just a junction for two circuits. one circuit is low current (the trigger) and the other circuit is your high current circuit (devices, etc driven from the battery/alternator)

when the low curent line gets voltage, it closes a switch in the relay to complete the second circuit, allowing whatever you're using the relay for to have it's 12 volt power delivered directly from the car's electrical system for more current, instead of being fed through the trigger circuit, like a head unit's REM wire, which can only supply around 250mA of current as opposed to the heavier wire from the battery that can supply several amperes.

[url]http://www.the12volt.com[/url] is the site ya want for relay diagrams.
that site has a ton of info on relay usage in car audio from simple multiple triggers for REM wires, to witing up power locks and windows to alarms.
gives the diagrams that are very easy to follow. I use it as a reference for a few of the more esoteric power lock systems in cars now and then. Easier and faster to look up work someone else already did instead of doing it myself. I'm lazy. hehe

Been reading bcae and decided its best for me to use a relay so I have a couple questions regarding just a Bosch relay.

Just connect me if im wrong on any of this...I will bold anything im very unsure about.

I would connect a wire from my + battery terminal, fuse it, and connect it to 87 on the relay. I want this relay to turn on with my HU, so I would connect my remote turn on wire to 86. 85 gets grounded. [b]Then I connect 87a with 30?[/b] And then how many different electrical accessories can I connect to 30? I plan on using two fans. But I may use more than one relay so I'd like to know how many for future reference. Then Each device I run off 30 has to be fused along that wire, with the proper rating for whatever size wire I use. When my HU turns on, the relay will have power and each device connected will turn on.