Automotive Wiring Diagram.Com Forum

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Things To Consider When Wiring Accessories...

When wiring anything in your vehicle that draws heavy current such as high powered offroad lights there are a few things to consider. Number one, make sure you use wire that is rated for the amperage that the accessories is going to pull. It is always better to have wire that is OVER rated rather than wire that is not rated high enough. If wire is used that is not rated to handle the current that your accessory will pull, the result could be overheated wires that could melt the insulation, causing a short or worse yet it could result in a fire. If you know how much current your accessory will draw you can determine what gauge wire is appropriate for your application.

Personally I like to use wire that far exceeds the current draw of my accessory. It's overkill but in a few applications I've used heavy gauge stranded industrial wire with water and chemical resistant insulation. That way there is no question as to whether the wire is rated high enough or not. If this approach is taken, it is very wise to place a fuse at the battery end as close to the battery as possible. Most wire in a vehicle, if shorted out, will burn up before the battery overheats and possibly explodes. If wire that is over-rated for vehicle use is used and a short occurs, a short will most likely result in damage to the vehicle of some sort unless a fuse is put in line as close to the battery as possible. With the fuse there, in the case of a dead short, the fuse will burn out first before any damage could occur.

With accessories that pull a lot of power it is always better to get your power directly from the batteries positive terminal rather than tapping into the existing fuse block or wiring harness. In most cases the vehicles existing fuse block is not rated to handle the additional load of high powered accessories such as offroad lights. If you are the kind of person that likes to add all kind of goodies to your vehicle it might be worth installing an additional fuse block that handles non-critical items like offroad lights, CB radios, power inverters, etc. This additional block can then be powered by a heavy duty wire capable of carrying the current required of all the accessories on the block. Be sure to fuse the block at the battery.

(from offroaders.com)