Heavy Duty 12 VDC Relay w/Connectors

Heavy Duty 12 Volt DC Relay w/Female Connectors

Using a Relay: 

The switch or control power only needs to supply a small amount of current to trigger your relay + (86) & - (85) ground. 
Put a switch in series with the + (86) trigger input to be able to turn the lights on and off.  This can even be a signal from somthing that is energized when your key is turned to on.
 

Hook up heavier wire thru a fuse directly from the battery or Accessory Fuse Panel to the in terminal (30).  Hook up output terminal (87) to your Lights, Load, etc . 
You are now running all of your current through the relay contact instead of a switch which may not be able to handle the load, and possibly burn out.

Light Bar Wiring Instructions