Help designing a sub harness powered from a relay?

[rjewkes]

This sub harness is a way to have 6 KC Lights 4 on a roll bar and two hanging from the factory bumper/push guards.

i want a seperate switch for these but want it to only be turned on if the headlights are on. I'm guessing they run 2-5 amps each so about 30 amps all together, would i want a 35 or 40 amp relay?

I'm also thinking of putting the cab lights on the roof on a relay. Currently the cab markers are on the same circuit as the running lights.

[fordman]

http://www.danielsternlighting.com/tech ... elays.html

[rjewkes]

Thanks Fordman.

[Sam I Am]

That's a good link, I didn't read all of it so this might be covered by Daniel Stern.
If you are running a separate switch and a whole new circuit for your add-on lights, you can put the switch on either the control + or -, the relay doesn't care where the switch is in the control circuit. You can put it where it is convenient for you.
I like to use a switch on the ground side. I run the control + after a fuse straight to the relay, and control the control circuit by switching the ground.

You can tap straight off an existing fuse, as long as you don't overload the original circuit the fuse is protecting. There are some really cool fittings that will keep the fuse in place and poke a spade out of the fused side for easy access.

I found some in stock at a local NAPA store.
Just remember to remove or insulate that fitting if the circuit is no longer needed so that there isn't a hot spade poking out where it shouldn't be. And don't overload the circuit. A control circuit for a relay doesn't draw much, so this is a really easy way to add stuff safely. Just run a dedicated power wire with its own fuse for the relay's "power" circuit. Make sure the light bar / roll bar is grounded, and ground each light fixture to the light bar.

To find which side of a fuse is powered and which side is fused, check the fuse with a test light to make it turn on and off with the ignition switch. Now pull out the fuse and test both sides of the fuse holder. With the fuse out, cycle the ignition switch and you'll see that one side of the fuse holder will be "Hot" and the other side "Not". Put the fitting on the "not" side to have that circuit protected by the fuse. Also known as "naught", as in zero.

FWIW, all the experienced off-roaders I know don't put anything on top. If they need more light, they use KC Daylighters behind a brush guard. As long as they are below the level of the original headlights, they don't have to be covered. Just don't get caught using them on the street! Anything above the level of the headlights is required to be covered in this state if you drive it on public roads. The trees and brush around here will knock off anything on top. But if you are only mudding or cruising marked trails top mount is fine.

Also, if you use LED lights for marker lights, they use very little juice so you can have a whole lot of them without overloading and they can be easily added to the existing marker light circuit.