Im not sure if anyone can help but I am wiring a motorcycle tail light and it only has 2 wires.... I need it to be brake and running tail light but I dont get why there are only 2 wires..... any help would be great, and it IS a tail light and brake light.... but only 2 wires. I will be hooking it up direct to battery and a brake switch.

thanks

should have one wire for the brake and 1 wire for the running/parking lights The bulb should have 2 filiments inside snd 2 contact points on the bottom of the bulb .. the bulb itself is grounded to the metal of the bike. Thats why you have 2 wires.

I don't get it- so there are TWO sets of lights (brake AND running light) and yet there are only two wires? There should be a set of wires for each light, unless that other light ISN'T a running tail light at all. And that's what I figure- the whole thing probably consists of a single tail light with NO running lamp.

Either that, or someone forgot to make provisions for that running tail light from the factory. If THAT's the case, you'll have to rig up a second pair of wires for those running lights or whatever, or take the offending unit back and get one that actually works.

Thanks for the help, that's what I thought at first ... Im gonna change where it is mounted and see if that helps ... thanks again!

One wire should be brake and the other tail light. Ground is through the chassis usually. Connect a multi tester to one wire and one to the frame and activate the brake and the light switch. That will tell you which wire is which.

Problem solved ! You do'nt need my help. If it still does'nt work check for a poor ground Or test the switches !

Ground is the chassis.

I meant to look for corrosion or paint or some other interference with the ground .

Well geez...if you were talking about changing out a ceiling fixture or an electrical outlet I might be able to help (because I've made the mistakes and figured it out!) Throw in a motorcycle and I'm LOST!

Bingo!

OK........

Changed the location and still dont work, if I connect one the wires to the battery one on pos one on neg it lights up, but does not change the brightness if u switch them and for some reason just will not light up the way it should. It is brand new..... but the main body of the fixture is painted black ... it was when I bought it...

should I remove some of the paint?

should I say F*ck it and go to a junk yard and get a new one?

Any suggestions?

Yes try removeing some of the paint on the suface where it mounts to the fender . Other wise start checking swiches !

No switches yet..... just trying to get it to light up the 2 filiments inside. Did it with the headlight, just trying to build up a little bobber.

Garage built look, so far I have....

stock 1978 Honda cb400 Hawk frame, flat black frame and tank, mini apes, harley hand grips that are not wired yet for anything. I had a guy trade me some screaming eagle II exhaust pipes and alot of other random parts like the controls, it has a solo seat I made and im looking for a white wall tire.

Also need to wire up the turn signals once I find a wiring diagram for these controls to find the right wires. Kickstart only for now.. just got a new battery from a 2007 dyna glide

Its my little project lol

Ok now thats a little clearer! Ok somebody said to check the number of filaments in the bulb did you ? Then you must have ground .First touch one wire to the positive on the battery and one filament should work then do the same with the other wire the second filament should light . Doi not touch one to positve and one to negative your only feeding back through the light then !

OK.....

I will try in the AM, I think since I have been adding so much stuff and kinda overlapping on it all, Im just gonna rip it all back down to the ground and start over and make sure everything is clean and done properly. I am just building this thing up for a bar hopper and then once I start getting more clients getting tattoos I plan on getting an old shovelhead to make into a nice ass bobber that I will keep and probably just keep this one until someone wants it

This may sound silly,, but.
since the headlight works, the battery is getting a good ground to the frame I would guess.
so, is there any reason the fender might not be getting a good ground to the frame?
touch tester to pos on the battery and on the fender(on any bare metal).. if you get the reading then you know the fender is getting grounded,
If not.. bare some metal where the fender bolts to the frame.
if contact points are rusted, can also stop the ground.

wiring should be coming from switches, not direct to batt.
Headlight switch for tail.
Brake lite switch for brake.
suggest you get a basic mechanic's book for wiring.
Training helps with this sort of thing.

You didn't mention if it was a Harley, Japanese, or British. The general instructions Durtyduck gave are true but British bikes have positive ground and the Lucas electrical systems are nightmares. Sometimes the connector plugs will loosen on a Harley and Jap bikes have grounding connection problems to the frame. The best test is to run a temporary ground wire directly from the battery and use it to check the lights. If it works then, but not while installed, you know you have a headache frame ground that can be difficult to trace. It is a good idea to trace all frame grounds and clean them well as regular maintenance. I learned the hard way. LOL

Side note: There is a new product called "Freeze Off" made by CRC. You spray it on rusted bolts and freeze them. The metal shrinks breaking the bond and the bolt comes loose. I used it this weekend on the oil drain of a '71 Triumph 650 that we had struggled with for several weekends. The stuff is amazing.

I have stripped off all the stuff I had done so I can start over. The bike.... is a 1978 Honda Hawk II

All the frame and motor is stock, although the frame is painted flat black. The battery I have is off of a 2007 Harley dyna glide and so are the controls. The tail/brake light is one from the store I bought for cheap, I think it was meant for a trailer, but it does have the 2 filaments inside one for running and one for brake.

I have basic mechanical knowledge and I have done wiring on many different projects. Just never on a bike before.

I have 2 - 3 position switches, just not sure if I wanna use turn signals or not. I have the one wired to the headlight but this bike runs a halogen sealed beam light and it looks kinda dim.

I am gonna be trying a few of the things right now once I get out back, thanks for all the help guys.

Ill keep u updated!

Bingo. Lots of aftermarket trailer lights have separate grounds because the ground won't go through the trailer hitch. I would pigtail the battery with a couple of leads, wire in the two power leads from the light (brake and running) then use the ground pigtail as a test lead to find the connection point to make it work. It probably is designed NOT to ground through the frame, but some are. Once you find the sweet spot, run a ground from that point to the frame and you are home free.