Using a headlight to load a circuit

I have a question. I have been reading a lot of articles recently that talk about using a headlight bulb to load a circuit. my question is;1) What is the purpose of this, 2) how are they talking about wiring it in, and 3) any diagrams would be appreciated into how to do this. Thanks.

Its for checking the integrity of a wire. Isolate the wire to be tested form any component, power source, or ground apply power to one end and connect the headlight bulb to the other end if the bulb shines bright the wire is good.
Be sure to verify the wire being tested is not shared with another circuit or shorted to ground before doing this.

Agree with LarryTheCarGuy, it's all about circuit integrity testing. I keep a 9006 headlight in my tool box for this exact reason.

For example, imagine a dead fuel pump. Brushes are trashed so there's no current flow through the pump. You've verified power and ground at the pump, but neither are loaded due to the dead fuel pump. You don't know if those wires will carry current.

That's where the headlight comes in. Put a bulb in place of the pump, and bam, you can now check pump power and ground under load. This same theory can be applied to most other circuits with some careful thought and consideration. You can also change up the size of bulb you're using based on the wire gauge and normal current draw of the circuit.

And to add, I have different wattage bulbs for different types of loads. Knowing how much current each type of bulb you use is important.

You wouldn't want to use a bulb that draws a low amount of current to test a fuel pump circuit and on the flip side, you would not want a high current bulb to test some computer controlled circuits. Measuring each bulbs amp draw is important.

I bought some high wattage metal cased resistors last month with the idea of making a puka dummy load up, I haen't had time to figure out the best way to use them yet it depends what I find in my junk box.

This topic has been moved to the Diagnostic Tools & Techniques section where it is more at home