Things to THINK about When Wiring Accessories…
When wiring anything in your vehicle that draws heavy current such as high powered offroad lights or audio amplifiers, 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
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
Where to Get your Power
The second important thing to consider when adding accessories is to determine where you will get your power. Many people will consider tapping into the hot wire of an existing circuit using something called a T-tap or quick slide connector, which are designed specifically for tapping into an existing wire. This is not always a good idea for several reasons. First and foremost, tapping into an existing circuit puts additional load on that circuit. The additional load placed on a circuit or wire may exceed the limits of those wires, connectors and fuse.
A better idea….
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 blocks, wires and connectors are not rated to handle the additional load of high powered accessories such as offroad lights and amplifiers. 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, audio equipment, 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.
Another important thing to consider is how you control the switching on/off of the power to your accessories. In almost every case where high current is required, the switch you will use to turn on the power should not handle the load because most switches are not designed to handle higher amps. The job of switching the power is better left to a relay. What is a relay? A relay is a device that, through a magnetic
The method I use for wiring the lights and other external accessories, for the most part, follows the diagram pictured above. As in the diagram a wire is run from a 12 volt power source to the switch in the cab and out to the relay placing a fuse at the source of the power. (Follow the relay’s wiring schematic when connecting the wires to the relay) One of the relays terminals goes to ground. Then run a heavy gauge wire from the battery to the relay placing a 30 Amp fuse in line very close to the battery. Do not connect the power to the battery until all wiring is done. Then I run a single heavy gauge wire out to the lights or other accessory. If installing lights, split it into two leads at the lights. If you do this be sure the wire is rated to handle BOTH lights since it will carry the current of both. The diagram shows two leads
Ohm’s Law Defined
Ohm’s Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.
( I ) Current is what flows on a wire or conductor. Current is measured in (A) amperes or amps.
( E ) Voltage is the difference in electrical potential between two points in a circuit. It’s the push or pressure behind current flow through a circuit, and is measured in (V) volts.
( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. The higher the resistance, the smaller the amount of current is allowed to flow. Resistance is measured in ohms.
( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.
V = I x R
I = V / R
R = V / I
Alternative Offroad Lights or Accessory Wiring Diagram Using a Relay