Single Filament Headlight Wiring

[tomiles]

Hey, looking for a wizards advice;

I want to hook up two single filament headlights to replace my dual filament head light. Not very competent with electricity.

Each single filament light just have one wire coming out, do i just need to cut the female three prong stock head light plug and attach running light to one, hi beam to another, and just find a place to ground that ground wire? or does each light need a ground spliced onto it?

When all is said and done, id like one light to be the running light and the other light engage with the hi beam.

Thanks!

PS. Lights are 12v and this is going on a 2003 sportster so just need to understand before i start soldering

[WillSCB]

If I am understanding what you want to do, you want to have one element as a low beam and one as a high beam. If this is what you are trying to do, you go to your factory wiring diagram to find out which wire is high, which is low, and which is ground. The ground you will want to split off into two wires, one going to each filament. The high and low will go to the corresponding filament. Hope this helps you out with what you are wanting to do.

[tomiles]

Sounds pretty simple but here are some further questions. These lights just have one wire running out, i read that some of these single filament lights are self grounded. I have taken the lights apart to see if there is a position to attach a ground wire and there is not. Are you saying i attach a ground wire directly to the single wire coming out, and attach another wire to either the hi/low wire? Can i attach the ground wires back to the ground wire coming out of the 3 prong female set up im about to snip off, or should i ground them to a washer, or even ground them separate? If they are self grounded then it should just be as simple as this diagram?

[WillSCB]

If it doesn't have a ground wire, it is designed to be put into an assembly that is grounded to the frame. Do you have a photo of the lights you are planning on using? Hard to tell what you have without seeing it. You will probably have to look inside the headlight assemblies, as there is most likely a wire grounding the lamp to the body of the headlight. If so, you disconnect it, solder a longer wire to it, attach the two wires from the two assemblies to the ground wire on the three prong plug. Another thing to look at is what wattage the lights are. If they are drawing more amps than your stock lights, you will need to go to a larger fuse or breaker. The math to figure this out is watts= volts x amps. So, to figure out amps you divide the number of watts to the number of volts (which is 13.2 in a 12 volt system.) So, for example. If you have two light units that use 75 watts a piece, assuming that it will run both when on high beam (which I believe it should from the stock wiring,) you divide 150 watts by 13.2 volts, getting an amperage of about 11.4 so a 15 amp fuse or breaker would be needed (allowing plenty of margin for voltage spikes.) If you have a photo of the light unit, please attach it, thanks.

[tomiles]

They are both 12V single filament lights. The guy i bought them from says they are self grounded.

[BlackCloudSalvage]

The lights are grounded by the case of the light bulb. So you have the metal cylindrical jacket at the bottom of the bulb, that gets grounded, while the nipple terminal at the base of that gets the 12v when connected into the socket. You can solder a ground wire to the sleeve that each bulb sits in and run that to frame ground or whatever if the case isn't already grounded. So you need a total of 4 wires. Hi beam wire to light (1) socket, ground wire to light (1) sleeve/case. Low beam wire to light (2) socket, ground wire to light (2) sleeve/case. You can splice the ground wire so it branches from a single wire out to both lights. The lights are only "self grounded" if the case makes a good clean connection to frame ground and is not isolated by paint or rubber/plastic washers, corroded bolts n washers, etc. I prefer a good wire ground on certain things.

[BlackCloudSalvage]

If you really want to keep it simple then just make sure your trees then like all you need to do is run the hi and low wires and bolt your mount to the triple trees and you'll be good to go.

[WillSCB]

Also, it looks like the copper tab just underneath the light bulb may be for grounding purposes, so you could attach the ground wires to that.

[tomiles]

So should i attach a ground wire thru the eye hole or solder the fuck out of it onto the light body? or where?

[BlackCloudSalvage]

Like will said above, you could attach it to the copper tab terminal seen in your earlier pic on the case of the light housing with a spade terminal. anywhere that will make a good conductive connection with the body of that light bulb. You don't have to connect the wire to the actual bulb housing, it just ultimately needs to make an electrical connection. Heck you could just attach the wire to the dual mount bracket. Either way, get yerself a cheap multi meter and do a quick 15 minute YouTube research on continuity checks, voltage checks, etc. Basic electrical knowledge will free u up so much with messing around with motorcycles. It's a must and is fun and easy once you start.

[BlackCloudSalvage]

The wire which touches the meral bracket which touches the metal headlight Case, which touches the metal bulb housing. It's one big electrical connection. Like one wire, only more areas for failure due to corrosion or lose connection, etc. Like mentioned above you could likely just not even run a ground wire since your triple trees share the frame ground (your battery negative has a big cable that bolts to your frame) so then your trees are grounded, your bracket will bolt to the trees and be grounded, etc as long as there is good clean connections. That is the "self grounded" he was talking about.

[tomiles]

so doing the bottom diagram and then mounting it directly onto the trees should be all i need to do then if im keeping it simple?

I am using galvanized brackets to attach to the top tree, a chrome wide glide bracket headlight bracket will be bolted onto the galvanized brackets, the head lights will mount on the wide glide headlight bracket.... Should be no able to sustain the ground?

Just take the head light ground and find an unpainted surface to ground?

[tomiles]

or should i take that ground and splice it and do it to the bottom of each headlight mounting hardware?

[BlackCloudSalvage]

Sounds like you got the gist of it. Give it a shot and get back to us.

[tomiles]

ill report after the weekend