Vehicle electrics these day are highly complex, with multiple computers controlling many items and procedures. Any attempt to dicker with those requires a fairly deep understanding of electronics. So, don’t!
However, especially with 4WDs, people like to add or change things. Once you go deeper than plugging to the ciggie lighter outlets you’ll need some understanding of basic electrical circuits. You were probably baffled, at high school, for instance, by Ohm’s Law. Now grown up and with experience of household appliances, vehicles, stereos, etc, it may be easier to understand, as it's actually very basic. Here we go:
Loop de loop!
You’ll probably remember that an electrical circuit is a loop, which is why it’s called a circuit. In that loop it has a supply of electricity – the mains…