For those who want to cleanly install HD fog lights on a 2010 Road King using the accessory switch in place of the cheap little plastic switch that comes with the fog lights.
You will need the following not included in the Harley Davidson Fog Light Kit:
1- 6’ of 14-16 ga. 2 wire ribbon or 4 wire trailer ribbon will work.
2- 2 blue butt splices.
3- Black electrical tape. I suggest Scotch 33
4- HD accessory female connector and two pin tubes
5- 8” of black 3/8” split flexible wire organizer plastic tubing

* Remove the fog light kit from the box and locate the wiring harness. Cut off the relay, fuse holder and switch and save to use for something else later.
* Cut the wiring harness where the leads to the fog lights split away from the body of the harness. Leave the shiny rubber wire covers on these leads.
* If you are using 4 wire trailer ribbon, split out the brown and white wire side of the ribbon the entire length of the wire.
* Split the brown and black wire about an 1”
* Strip the brown and white wires about ¼”
* Strip the four wires with the bullet ends ¼”
* Twist the two black wire ends together
* Twist the two white wire ends together.
(I twisted and soldered mine)
* Slip the twisted ends into one side of the butt splice and crimp
* Do the same with the other set
* Slip the brown wire from the ribbon into the other end of the butt splice with black wires and crimp
* Slip the white wire from the ribbon into the other end of the butt splice with the white wires and crimp
* Tightly wrap electrical tape around your butt splices and about one half of an inch both ways from the splices.
One end of your new wiring harness is now complete
* Remove your seat by removing the screw that holds the grab strap on the left side of your bike. (You will probably have to open the lid on your left saddle bag to access the screw.) Remove back rest if you have one. Remove the screw on the back of your seat and pull the seat back and up to remove.
* Remove the covers on your front gas tank mounts. These, slip off
* Under the left front side of your gas tank is an electrical connector. Locate it and unplug it.
* Unhook your fuel line. This works like a quick connect on an air line. Pull the sleeve down and pull down on the lower black part of the line from the connector.
* At the back of the tank, locate your tank vent line. There is a rubber boot on it. Pull your vent line from the rubber boot.
* Lay a soft thick towel on your back fender and saddle bag tops
* Remove allen screw on front of center speedometer strip on front of fuel tank
* Remove bolt from back of center strip located between two back tank mounting bolts
* Gently pick up center speedometer strip and unplug connector to fuel sending unit.
* Leave main wiring harness attached and set center strip assembly out of the way on the towel
* Remove both front tank mounting bolts
* Remove both back tank mounting bolts
* Remove tank and set out of the way
* You will see a long black plastic wire way on the back bone of the frame. Pop the top off it and set aside
* At the front of wire way, you will see black rubber wire cover tucked into the wire way. Pull it up and remove electrical tape from it
* Turn your handlebars to extreme right and locate the front of the wire cover at the front of the frame behind your headlight shroud.
* Insert the unspliced end of your new wiring harness into the front of rubber wire cover and feed it through the cover into the wire way and back to where your battery is located.
(The wire will be longer than you need but leave it long for now)
* Pull the spliced end down to where the split is at your engine guard.
* Go ahead and loosely mount your fog lights onto the guard. I located mine 8” from the engine guard top mounting bolt.
* Plug bullet connectors into the corresponding connectors on your fog lights.
* Slip the split flexible wire organizer onto your wire harness so it covers your splice and up the wire and just into the rubber wire cover.
* Locate the wire cover mounting strap and use a zip tie from the kit to pull excess wire up and out of the way so it is clear of being pinched when you turn your handlebars.
* Hide your wires coming from your fog lights on the bottom of your engine guard and zip tie them to engine guard at the fog lights and as close to the top engine guard mounting bolt as possible.
* Retape the back end of the rubber wire cover with electrical tape and place back into the wire way.
* Lay your new wiring harness neatly in the tray and replace the wire way cover. (I put two extra new wires in so I don’t have to pull the tank if I choose to add something else later.)
* Locate your existing accessory plug. It should be a black male connector with a rubber cover inserted into the end of it and it should be hanging loose in front of your battery box. It looks just like the connector located at the bottom of your fuse panel that HD uses to hook up a diagnostics computer to your bike.
* The connector will have 3 orange wires and one black wire going into it.
*Locate the black wire and the orange wire directly below it. These are the two wires you want to attach your new fog light wiring to. Pull your new harness end to the accessory plug and cut the new harness wire about 3” longer than you need. Strip both wires ¼” back and slip into new pins and crimp. (I soldered mine.)
* Slip the pins into the back of the accessory plug you purchased from HD in the locations corresponding with the black and orange wire on existing connector. Push the pins in until they snap into place.
* Plug the new end into the existing end.
* Replace your gas tank and don’t forget to re-attach the plug on the front left bottom of your tank.
* Plug your sending unit back in on your center strip assembly and replace the assembly. Replace vent line into rubber boot. Liquid soap makes it easier to slide in.
* Turn your switch on and close the accessory switch to test your new lights.
* Replace your seat and back rest and you are done.

Some of you might be wondering why HD would include a relay and fuse holder if these are not needed. Your accessory switch comes from the factory prewired and fused so the fuse holder is not needed. A relay is simply a device used to allow a cheap little low amp switch like comes with the HD Fog Lights to open and close contacts in a higher amp circuit. Your existing accessory switch is good for about 20 amps and your fog lights only draw 9.1 amps so you are safe.
To better understand how a relay works, it is solenoid that opens and closes a set of larger contacts that will make and break a circuit. A solenoid is a device with coil and a sliding core attached to one side of the contacts. The HD relay included with your kit allows the little 2-3 amp switch to energize the coil which moves the sliding core up or down to make or break the contacts in the circuit between the battery and your fog lights.

 

About 2 years ago I put fog lights on my '08 Street Glide and installed a "Spot" switch. I was unaware of the plugged "Auxillary" connector at the base of the seat in front of the batterty. The fog lights gave fantastic lighting of the road at night. As I am going to San Francisco in a couple of weeks and will be riding out of town at night, I wanted to install fog lights on my '09 FLTRSE3.
After reading your posting I installed the fog lights by connecting to the plugged "Auxillary" connector. However, after cutting off the relay and push button switch and removing the excess wires, I ran the remaining 4 wire bundle up over the front of the gas tank and ran the wires under the console down to under the seat area. The bundle was securred to adjacent wires with ties. Then I cut the four wires, twisted the white and black wires seperately, and connected to the respective colored #16 gauge wire with blue connectors. These pieces of black and white wire were only about 4" long. Deusch female pins were attached to the other ends of the short wires which were inserted into the corresponding pins hole of a 4 hole female Deutsch connector. After assembling the connector the lights worked perfectly using the auxillary switch.
This method avoids having to remove the tank.