Wiring a Lightbar Using a Relay (James92026 from the Kawasaki Vulcan forum)

Lights diagram using a Bosch relay

The fused lead from the battery should go to post #30 on the Relay

The ground wire should go to post #85 on the relay. (I would use a dedicated ground wire rather than a nut in the shell) any black/yellow wire is usually ground.

The switched power source (or common headlight feed) should go to post #86 of the relay. This one will have your lightbar switch in-line. You mentioned using one of 3 wires going to blinkers. One of these would be running lights and is the one you should use. It will probably be Red/Blue.

The remaining post #87 goes to the driving lights. (I would place a fuse here also)

You need to switch the ignition on. If you used the headight "feed" you need to either start the engine or at least bump the starter until the headlights come on.

The current flow goes like this: Source power through the lightbar switch goes to #86 which powers a coil which then pulls an interior switch (electromagnetic) to the other side of the relay and connects #87 to #30 and hence your battery.  Think of it as a teeter-totter where a small effort on one end can lift a much larger load on the other.


edit: The circuit shown in the link has pins 85 and 86 opposite of what james said - to be clear, there is no polarity on those pins, meaning it doesn't matter which of the two are ground or 12v - either way - power across those pins turns on the relay.