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Old February 3rd, 2006, 09:56 PM   #1
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Right Way to Wire off Road lights

here it is to many people wire light wrong and ask this qustion to many time. When wiring light make sure you have the right wire to handel the volts 10 Gauge is suitable for off roadlights the relay can be had at Autozone or napa I used the Baja 30 relay.

anyone wants to add to this Please do so.

Please sticky

Originally Posted by Haggar
Here's the math of it:

You have a 130 watt light. Generally, automotive bulbs are rated at nominal 12.0 volts, whereas you probably have 13.8-14.4 when your car is running.

OK, 130 watts/12 volts = 10.833 amps. 12 volts / 10.833 amps = 1.1077 ohms impedance of the bulb.

Working backwards: 13.8 volts / 1.1077 ohms = 12.46 amps.

times two, since there are two lights, thats ~25 amps load.

For main wiring in a vehicle of a that run length(factoring in that the run is not bundled inside a full harness which reduces capacity), usually OEM size would be 12 gage, although I prefer the old standards and would run 10 gages for anything between 20 - 30 amps steady load.

The best setup would be to run a relay setup up like this:

There are two terminals to the coil. One side would connect to battery through a small fuse. This size depends on the coil resistance. Probably a 3 amp fuse is just fine. The other terminal of the coil would go to the one side of the switch. The other side of the switch would go to ground.

Then for the main contacts, one side would connect to battery with a 30 amp slow blow fuse, and appropriate wire size. 12 gage would certainly be acceptable here if your wire length is short(i.e. mount the relay close to the battery). The other terminal, I would branch off two 14 gage wires to feed the two lights.
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Last edited by ksejeeper; February 3rd, 2006 at 09:59 PM.
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Old February 3rd, 2006, 10:46 PM   #2
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