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Discussion Starter · #1 ·
In the second part of this series, we'll talk about basic wiring configurations for your fog lights.

Let's start off with the 2 basic circuits, series and parallel circuits.

A series circuit is when you have all your devices attached in the same chain. The current coming out of one device feeds the next device. This is not such a great circuit because if one of the devices in the circuit fails, the circuit is opened, electricity has no where to go, and everything on the circuit fails. Like a cheap set of Christmas lights, when one of the bulbs burn out, all the lights don't work.

In the example below, the burnt out light bulb would prevent the good bulb from operating.
 

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Discussion Starter · #2 ·
A parallel circuit is when you split the POS wire and each device has it's own connection to the POS. So if one of the bulbs in the example burns out, the other bulb will still be operating because it has it's own feed.
 

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Discussion Starter · #3 ·
How do you determine which wire is the POS and which is the NEG?

The NEG wire is usually black or white, and the POS wire is colored (ie. orange, blue, green, red, etc.).

If one wire is black and the other is white, then the black is NEG and white is POS.
 

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Discussion Starter · #4 ·
There's 3 basic ways of hooking up your fog lights. This first method is HIGHLY discouraged because you may melt the wires.

This is the method you are lazy @ss [email protected], who's too lazy to do any wiring and want your fogs to come one when you turn on the driving lights. Some people hook up their foglights directly into the POS of their driving lights.

This is bad. Because the current and wiring that is going to the driving lights are meant for running a 8 watt bulb. Taping into the circuit and hooking up a 55 watt fog lamp will put a strain on the circuit and overload it. It will draw too much current through too little wire causing the wire to overheat and melt.
 

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Discussion Starter · #5 ·
The second method is slightly better where you're directly tapping into the POS of the battery, and running a switch and a fuse.

The problem with this method is that you may sometimes forget to turn on, or worse, turn off your fog lamps because it's separate from the rest of the car's electrical system. Plus, eventhough you will be using a fuse to prevent damage from a short, some switches have a lower tolerance than a fuse. With a direct connection to the battery running through the switch, the switch may get damaged.

I wired up my first set of fog lamps this way on my old Camry, and my switch overheated, burnt, smoked, and almost caught on fire.
 

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Discussion Starter · #6 ·
The best way is illustrated below.

In order for the foglights to come on, the lower circuit needs to be closed. The driving lights must be turned on to provide power for the lower circuit, and the switch must be closed. The lower circuit must be complete. When the electricity can make its way from the POS of the driving lights to the ground, the switch in the relay will close, allowing the electricity to flow from the POS of the battery to the fog lights.

Let's say you forget to flick the foglight dash switch to operate the foglights. Doesn't matter. Say you leave the switch in the closed position. Well, just by turning on or off the driving lights will operate the fogs. Remember, electricity has to be flowing through the resistor in the realy to close the swith in the relay to complete the circuit that the fog lights are on.
 

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Discussion Starter · #7 ·
I'll be writing up.....

Fog Light Wiring for dummies Part 3/3: 2001 factory fog rewiring

...over the weekend when I get a chance to take pics of my install.

Watch out for the final part.
 
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