Intermittent headlight failure. Need ideas. - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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Where does this wire go?
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post #1 of 10 (permalink) Old 09-11-2015, 06:57 PM Thread Starter
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Intermittent headlight failure. Need ideas.

So the other night my headlight, and only my headlight, went out. There seems to be no rhyme or reason why it's turning on or off.

I checked the fuses and they seem to be good if old and looked for obvious wire issues under the seat (found a black widows nest with alive spiders. no fun).

I replaced the newer slightly brighter bulb with the older one and got no change in weirdness.

Thoughts?

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post #2 of 10 (permalink) Old 09-11-2015, 10:09 PM
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I would think maybe a short if it's that intermittent and the obvious issues were checked for. Other than that could be an issue within the JB? slim will probably have a more detailed analysis.

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post #3 of 10 (permalink) Old 09-11-2015, 10:12 PM
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Try the headlight bypass mod.

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post #4 of 10 (permalink) Old 09-11-2015, 10:13 PM
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Quote:
Originally Posted by Sean Karp View Post
So the other night my headlight, and only my headlight, went out. There seems to be no rhyme or reason why it's turning on or off.

I checked the fuses and they seem to be good if old and looked for obvious wire issues under the seat (found a black widows nest with alive spiders. no fun).

I replaced the newer slightly brighter bulb with the older one and got no change in weirdness.

Thoughts?
You may have a problem with the headlight relay. Do a search here for the " headlight relay bypass ". Simple to do and if the light comes on your problem is solved.

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post #5 of 10 (permalink) Old 09-15-2015, 10:59 PM Thread Starter
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Quote:
Originally Posted by JM2001 View Post
You may have a problem with the headlight relay. Do a search here for the " headlight relay bypass ". Simple to do and if the light comes on your problem is solved.
OK. I checked the Hi/Lo switch. And it was in shape.

It seems to happen shortly after I start and can come back on without warning. So I figure I'll check the junction box & examine the relay.

I assume that the reason for the bypass solution is that the relay isn't on non-US/Can bikes and doesn't affect usability much?

"For practice is better than art. Your exercise does well without the art, but the art is not much good without the exercise." -Hanko Dobringer, 1389
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post #6 of 10 (permalink) Old 09-16-2015, 05:23 PM
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Quote:
Originally Posted by Sean Karp View Post
OK. I checked the Hi/Lo switch. And it was in shape.

It seems to happen shortly after I start and can come back on without warning. So I figure I'll check the junction box & examine the relay.

I assume that the reason for the bypass solution is that the relay isn't on non-US/Can bikes and doesn't affect usability much?
The relay just keeps the headlight off during startup (the voltage from the stator turns on the headlight). Bypassing it means the headlight is on whenever you turn on the key. A lot of bikes are like this (my VFR's lights turn on right away), but the VN added that relay to give extra cranking power. Not a big deal with modern AGM batteries though so safe to bypass imo.
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post #7 of 10 (permalink) Old 09-20-2015, 12:27 AM Thread Starter
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OK. So it looks like the headlight is behaving again after doing the blue wire relay bypass. This means that the relay is bad right?

Also there is a plug right below the junction box that is a bit disolved on top. WHat is it and how can I patch the issue/ stop it from getting worse?

"For practice is better than art. Your exercise does well without the art, but the art is not much good without the exercise." -Hanko Dobringer, 1389
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post #8 of 10 (permalink) Old 09-23-2015, 03:44 AM
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You may have some interfering corrosion/loose connectivity in the junction box where the headlight bypass relay is located rather than a bad relay per se. When an electrical relay goes bad, it is usually all or nothing, and not an intermittent short type of problem. Try cleaning any road grime or corrosion in that junction box area and maybe silicone patch that funky dissolved spot on the top of the box. That may lend to intermittent moisture problems etc. The headlight only pulls 55 watts on low beam anyway if on during starting. Your blue wire bypass sounds like a decent fix for now. Good luck.
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post #9 of 10 (permalink) Old 09-23-2015, 09:48 AM
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The spades in those plugs at the JB can get loose over time. Had to pinch them tighter on mine to get the fan working. Have to release them from the plug, then squeeze them slightly with pliers.

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post #10 of 10 (permalink) Old 09-23-2015, 11:03 AM
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Thought this was worth adding, since you've already had electrical problems. I'm recommending this JB bypass to everyone as a preventative measure. Needs written up into a sticky.

The wires in this bypass have been proven linked to: Start button - failure to function, Charging system- brownouts, failure to charge, lower peak charge voltage. (possibly another I'm forgetting)

Quote:
The Fix: Clipped two wires off the 10-pin JB plug: black/ red and yellow/red, spliced these two together. Note: this will bypass neutral and clutch lever safety start switches
In at least three recent discussions, this bypass has cured problems on 3 bikes, on one other, it failed to help. It's so easy to do, and can't hurt unless one can't ride without nanny switches.

1) Mine with a dead start button and charging brownout/low peak charge on a new TPE/MOSFET system. Start button fixed and peak charge increased by 1v to 14.5v, no more brownouts to 12.5v.

2) michiganteddy bear, Start button function restored. (he did this bypass before I did)

3)thtanner, new TPE/MOSFET not charging at all, restored to 14.5v (did the bypass last weekend)

Here's the thread where I did mine: https://www.vn750.com/forum/19-electr...wont-work.html

thtanner's thread: https://www.vn750.com/forum/19-electr...-replaced.html

michiganteddybear's thread: https://www.vn750.com/forum/19-electr...-cranking.html
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__________________________________________________ ____________
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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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