Continuity between positive and negative at headlight bulb?

[section8joe]

My bike runs great at idle to about half throttle then the headlight get dim and the bike runs like crap until I let off the throttle. I thought my charging system had issues until I disconnected the entire system and ran the bike from the battery only. I was still having problems. Voltage wise everything seems great. Should I have continuity between the positive and negative terminals on my headlight? I'm thinking no. I checked a few taillights that I have laying around and they don't have continuity. If it possible to have a running headlight at idle to half throttle only to have it die beyond half throttle because of this short?

Here's link to the headlight I'm using.

 

[Robhall]

No continuity between connections on an incandescent bulb means the filament is burned and the bulb is no good. Bad battery maybe? What charging and ignition systems are you using?

 

[section8joe]

I tried two batteries, I'm running a pma and the headlight still works but it does have continuity to ground. They're should be NO continuity to ground right?

 

[Robhall]

Do you mean just testing continuity between the terminals when the light is unplugged?

 

[section8joe]

Yep. Just to the terminals with no wires

 

[jayel]

yes it will show continuity because it's inter-connected in the headlamp itself, reading between yellow or green to black will read because both are connected to black, reading yellow to green will read thru both filaments, the headlight plug-in can back read thru the wiring and switches too,

 

[section8joe]

If thats the case wouldn't my brake light have the same reading? I have no continuity with the brake light.

 

[Robhall]

Is it LED?

 

[section8joe]

I actually tested a led tail/brake light and and regular 1157(?) taillight and there is no continuity between power and ground.

 

[Robhall]

Are you sure they're good? I'm not positive for LEDs, but I know incandescent bulbs should have continuity unless they are burned out.

 

[section8joe]

The incandescent bulbs were actually out of the taillight now that I think of it. I'm an idiot! I'll see if I have any when I get home and retest.

 

[XSLeo]

That headlight is just one beam right. With the bulb unplugged, testing continuity from just the two wires, you should get continuity from the ground wire to the frame/battery. If you have continuity from the hot wire to ground, then you have a short to ground on that wire.
Leo

 

[section8joe]

The headlight is just one beam. I unplugged the bulb and tested the actual terminals on the bulb and they have continuity.

 

[XSLeo]

Ok with the bulb unhooked then yes, it should have continuity. If no continuity the power can't flow through and light the bulb.
Your bulb is good. If you are having problems then the headlight isn't one of them.
Are you running a PMA? Punkskalar is working with some others on a simular problem. Might want to ask him about it.
Leo

 

[section8joe]

I do have a pma and I completely disconnect the charging system and ran the light and bike straight off a battery. I still had the same problem. I rewired the bike hooking up the charging system and ignition only. The bike runs great. I do have a dead spot at half throttle. I think that's carb related. Bike runs great except for that dead spot. I'm going to mess with the carb a bit them try to hook up some lights.

 

[XSLeo]

If it runs ok on just the battery, then ok on just the battery and PMA, but had trouble when you hooked in the lights, then your lighting circuit is the problem. We have decided the headlight itself is ok.
I would at this point give the lighting circuit a good going over. A short in there maybe hard to find. Anywhere the wires can rub can be a short. Where the wires pass into the headligt bucket. Tail light socket.
Leo

 

[section8joe]

Yeah I'm going to hook up the taillight, make sure that works ok, the the headlight. I'm also using all new wire. Last time I used old wire from the existing harness for the ignition line. I'll let ya know how it goes. Thanks!!

 

[section8joe]

I was running the bike with just the ignition line hooked up and I have a little carb related flat spot and the bike seems to run fine. I tried to hook up the headlight tonight and I'm having the same problem. Keep in mind that this is all new wiring. Can the headlight work and still be problematic? Can the problem lie with my ignition switch? I have a spare and I'm going to throw it on tomorrow and see what happens.? I tested resistance between all three terminals on my switch and they all pretty much at 00.0. Any other ideas? Ingition coil seems to test fine too.

 

[XSLeo]

If it runs ok with everthing but the headlight. Then it has to be in the headlight wiring.
Is your ignition switch set up as off/on/on with lights? Older Harleys were that way.
If you have a seperate headlight switch check to see if there are any loose wires inside that could be shorting.
Leo

 

[section8joe]

I ran a new wire(16 gauge) from the ignition switch to the headlight. I also ran a new ground at the headlight. My switch is an off/on/on with lights. When I started it up and revved it the lights still dimmed. When I took it for a quick road test the bike fell flat on it's face. I restarted the bike and it ran but not great. The bike seems to run ok when the lights are hooked up but in the off position. When I tested it last night it was dark out so I really couldn't ride it with the lights off. My problem has to be the "on with lights" or my headlight. I hookup up a new switch today. When I rev the engine the lights seem to be a bit better. The headlight still dims(a little) at what seems to be redline. I'm afraid to hold the wide open throttle while the bikes in neutral in the garage. I don't want to blow the engine. I'll have to wait til tomorrow to take it on a test ride since it's raining here today. I also didn't take any voltage reading with the light hooked up. I'll have to do that tomorrow too.