[Snitty]

to wm69.... relays can be very very helpful tools... i don't wire anything anymore without them.

here is what they do... instead of running the power for a device through the switch in your dash... it will run through the relay... if you have 4 100 watt lights on a light bar, you dont' want that current running through your dashboard... you are liable to be chasing melted wires and burning your fingers on a red hot toggle... if you run a relay... that relay, which is designed to handle higher current, will take all the current... the dash switch will simply be handling enough current to activate an electromagnet inside the relay which closes a switch inside to complete the higher draw circuit...

if you want to use them for their basic use... follow this simple list...

85- power from switch (or former power wire)
86- ground
30- fused, direct 12v power, usually 12 or 10 gauge
87- device to be powered when the switch is on
87a- device to be powered when switch is off

not all relays have an 87a... and if you are simply using one device, you need not use 87a at all... it is simply used as a "selective option" so you can have the option to power one device with the switch on, and one always powered with the switch off...

some relays are directional... and the 85/86 poles must be wired in a certain polarity... if a relay doesn't work, and seems like it should... always switch the 85/86 poles to see if that takes care of the problem.

a common error that people make while hooking up relays is forgetting to ground the relay coil, which is the electromagnet in there... when you flip the switch, the relay needs THAT power, and a ground in order to activate the internal switch... remember that both the relay AND the final device need to be grounded