Originally Posted by rickyj

The original poster should use a higher gauge wire if for no other reason than it is easier to work with. But it isn't going to catch on fire if he uses 20 gauge wire. My original recommendation was probably not the best one but it was late and I was tired. You can always use a higher gauge with no ill effect. But will it work? Sure. I am surprised by a forum that doesn’t give a second thought to pulling federally mandated rollbar padding, drastically changing the forces on the hub bearings with non factory backspacing or wheel spacers, or bumpers that change the impact pulse of a collision is so freaked out about wiring. I am guessing this is a waste of time, but I have so much time right now I might as well waste it.


Using 20 gauge wire the total resistance for a 10 foot section would be 0.1036 Ohms. You can calculate the heat disapated by the wire in Joules with E=(I^2)*R*t. So if you left the lights on for 10 hours straight, that would be about 250 BTU per light. For the whole set of 6 that would only be 1500 BTU, so if you managed to put all of that heat inside of a 5 gallon bucket filled with water that leaked no heat the entire time you would only be able to bring that water from 70 degrees to 105 degrees. For 10 hours of on time. So dusk to dawn. Of course, the wires are going to be losing heat the whole time, so it isn’t going to catch on fire. I believe, if the JK heater is 60,000 btu (probably higher as it is a kick ass heater) it would put out the same amount of heat in 15 minutes, probably 10.

Disclaimer – I am not an electrical engineer, but I did consult my brother who is close to being one and he thought it was OK (as in work but not ideal) as well. But it was quick email, and most of my calculations were self taught in the past 30 minutes or so.
Back to the original question – just use 14 gauge or something.

Originally Posted by rickyj

The original poster should use a higher gauge wire if for no other reason than it is easier to work with. But it isn't going to catch on fire if he uses 20 gauge wire. My original recommendation was probably not the best one but it was late and I was tired. You can always use a higher gauge with no ill effect. But will it work? Sure. I am surprised by a forum that doesn’t give a second thought to pulling federally mandated rollbar padding, drastically changing the forces on the hub bearings with non factory backspacing or wheel spacers, or bumpers that change the impact pulse of a collision is so freaked out about wiring. I am guessing this is a waste of time, but I have so much time right now I might as well waste it.


Using 20 gauge wire the total resistance for a 10 foot section would be 0.1036 Ohms. You can calculate the heat disapated by the wire in Joules with E=(I^2)*R*t. So if you left the lights on for 10 hours straight, that would be about 250 BTU per light. For the whole set of 6 that would only be 1500 BTU, so if you managed to put all of that heat inside of a 5 gallon bucket filled with water that leaked no heat the entire time you would only be able to bring that water from 70 degrees to 105 degrees. For 10 hours of on time. So dusk to dawn. Of course, the wires are going to be losing heat the whole time, so it isn’t going to catch on fire. I believe, if the JK heater is 60,000 btu (probably higher as it is a kick ass heater) it would put out the same amount of heat in 15 minutes, probably 10.

Disclaimer – I am not an electrical engineer, but I did consult my brother who is close to being one and he thought it was OK (as in work but not ideal) as well. But it was quick email, and most of my calculations were self taught in the past 30 minutes or so.
Back to the original question – just use 14 gauge or something.

Originally Posted by b5rider

Thanks for the info. I am going to link the 4 lights on the rack to one switch and the other two to another switch. I am understanding that I can splice only the switch wires together, but I will run separate wiring and relays to each of the pairs. two more questions:

1 how do I wire the four rack lights to the high-beam switch? can I use the fuse box mod? If so, how do I wire the two circuits together to the single fuse?

2 how do I wire the 2 bumper lights to the fog switch?

Originally Posted by b5rider

Thank you for all the great info. I will take into account all the info and wire the lights next week. I am going to use the wires that came with the set and wire 4 to one switch and 2 to another. They are 55w lights and I will use them sparingly for no more that 1 hour, as I live in a suburban area. I mostly want them for when I go wheeling at dusk when there are motorcycles and mountain bikers out, so they need to see me.

Originally Posted by b5rider

Thank you for all the great info. I will take into account all the info and wire the lights next week. I am going to use the wires that came with the set and wire 4 to one switch and 2 to another. They are 55w lights and I will use them sparingly for no more that 1 hour, as I live in a suburban area. I mostly want them for when I go wheeling at dusk when there are motorcycles and mountain bikers out, so they need to see me.

Originally Posted by JK-Ford

b5rider- I hope that this thread did not become totaly confuseing for you. I do enjoy trying to help my fellow Jeepers in the areas that I know something about. Anyway, I drew a little design for you to Illistrate ( I believe) what you are looking for.

Attachment 69925

This design will handel a maximum of 150 watt Lamp per fixture.
Conductors from the battery are #10 awg. Each one has it's own 30 Amp Fuse.
Relays are standard 30 Amp 12 volt
Control wire should be feed from an ignition power source in the fuse box.
Control wire should be #18 Awg and have it's own 5 Amp fuse.
Conductors from the relay to the lights should be #14 awg minimum.
You do not need a fuse after the relay
Ground conductors from the light may be grounded on the frame. However, the return path is every bit as important as the supply path. So ground at the battery.

Hope this helps. Once again sorry for the confusion. Just ask and I will be happy to help.

Originally Posted by tHeKiNgMaN

Great wiring diagram! Anyway you can make it bigger? Grounding wires are recommended to be as short as practicle, but I've yet to see an issue running to the battery. Although the relay is rated for 30AMP you can get away with one wire size instead of two if you run #14 or #12 to the relays from the battery as well as to the lights from the relays. I also agree that control power should be run of ingnition and not constant. I've been the sap in the parking lot before with a dead battery because of that. Do it right the first time I always say... now...

Originally Posted by JK-Ford

Sorry to contradict. Ground wires for the switch and the relay are no big deal. However,

Secondly, I designed this system to handel 150 watt lamps so:


( 1 ) 150 watt lamp pulls ~ 12.5 amps. And #14 awg wire is good for 15 Amps
( 2 ) 150 watt lamps will pull ~ 25 amps. So the relay is rated @ 30 amps

Sorry I do not know how to mak the drawing bigger. PM me with your e-mail address.

Originally Posted by OnBelay

I guess one would have to compare the Specific Heat Capacity of the wire's sheath versus that of water (H2O has a SHC of 1 BTW). BTUs can have drastically different effects on different materials.

I don't worry about frying wires so much; I just worry about Amps and voltage drop.

Cheers!