Fog light wiring help
 

I just purchased a light bar and hella fog lights and I have some questions about how to wire it all up. I have attached the diagram that came with the fog lights (sorry its sideways). What I dont understand is the wire that connects the switch to my driving light? I guess its supposed to use that for power for the switch or something? How am I supposed to hook that up, and why wont the connection to my battery at the relay power the switch?

Of the two options for installations which one are you going to use? The second simply has a switch so that when you turn on your brights the axillary/beams can be toggled on and off.

So with or without the extra switch, I believe the solenoid is being energized from the headlight/bright switch or wire.



The switch simply powers the solenoid to energize the lights from the battery connection. That connection is fused and it's done that way for safety.

I recommend putting all aux lighting on switches. This is how the entire circuit works:

The switch has a ground, a power in, and a power out. The ground wire goes to a grounding nut on the body of the jeep. The power in comes from a power that SHOULD be controlled by the ignition switch (I say SHOULD so that you can't run the lights with the jeep turned off). The power out goes to the relay. This is what powers the relay to turn on the lights. For the ignition power, I ran mine from the cig lighter/aux power plug on the bottom left side of console below the climate control unit. I have a 2010 Unlimited JK and I have two. The right is connected to the battery, so it has a battery symbol on the cover, the one on the left is controlled by the ignition. I just used a jump splice to tap into the power.

So, looking at the diagram on the switch (right) side, position 1 will come from the ignition controlled power source (the power in), position 2 goes to the relay (the power out), and position 3 goes to ground.

The power that goes from the battery to the relay ONLY powers the relay when the it is turn on, this is done by the switch. That is why the power from the battery to the relay won't power the switch. You're thinking backwards. The power goes from the switch to the relay, not the relay to the switch.

Think of your switch as an on/off button. You have the battery power going into the relay and the lights attach to the other side of the relay with the button in the middle. With the button off it cuts the power that goes from the battery to the lights. When turn the button on it supplies the connection between the battery and the lights giving the lights power.

I did a lot of research before I started hooking my lights up. What I found is that to supply power to the switch from a source controlled by the ignition, you need a power source that isn't run by the computer. I don't remember the specifics off the top of my head, but something about the computer detecting a draw that shouldn't be there and possibly frying the computer. I'm sure someone else here could elaborate more on it.

Hope that give you a better understanding of how it all works and the way the current flows :thumbsup:

The relay needs two power sources, main power for the lights (20 amp fuse) and relay coil power (3 amp fuse) to operate the relay coil. The switch turns the coil on or off which in turn provides power to the lights.

State law regulates auxiliary lighting, check your state laws for specifics. Most say lights cannot be mounted higher than the headlights & not more than 4 lights, including the headlights can be on at once. Light bars, above the windshield or lights mounted on the a-pillar are off road only.

If you want to always turn the lights on/off only with the switch wire both leads to the battery. Beware, this means you always have to turn your lights off manually when you turn your jeep off.

If you are going to connect the switch to your jeep wiring,eg: at the head lights, to use your factory switches, then you have to add two diodes and a capacitor to protect the relay & the computer. SMS (rallylights.com) can provide an overlay harness to hook up all your lights & protect your computer as well.

Wow thank you guys for the replies, that really helped clear a lot up for me. I found the wire that I'm supposed to use to power the switch and I believe that it has a capacitor (pic) so it shouldnt matter from where I get the power? I was thinking of just running the power for the switch and relay from the battery? And as I understand it the only down side to that would be that I could kill my battery if left my fog lights on when I turned the jeep off? And final question, do I really need to ground each fog light or will a ground at the relay and switch be enough?

That is just an inline fuse, not a diode or capacitor. Every wire that supplies main power should have a fuse in it. That protects the vehicle if there is a short in the system so you don't fry something.

You can very easily supply all the power from the battery if you want. However, if you ever take your doors off any Joe Shmo can walk over to your Jeep if you're out, flip all your switches and kill you're battery if you're out shopping or even at night if you're in bed. Hence the reason I HIGHLY suggest using an ignition controlled power source.

As for grounding, yes. Both lights have to be grounded because the ground wire on the relay is just for the relay. You should have 4 grounding wires. One for the switch, one for the relay and one for each light (2). If you need to make your grounding wires longer so they reach a grounding nut, use 16 gage wire. Remember when it comes to wire size, the smaller the number, the bigger the wire.

Sweet, thanks for your help! I just finished up installing everything and it works great!