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Discussion Starter #1
Thursday night as I was on the way home from work, I stopped for gas about 6 miles from home. When I cranked the bike, my headlight did not work. All the other lights worked. I called my wife, turned the flashers on and followed her back home. Today, I removed the sealed beam (the plug was tight) checked the bulb and it had continuity. I then cranked the bike and I had voltage in the plug. I plugged the light back in and it worked. Anyone have any ideas? I don't need the light to go out when I am not in as safe a place as I was the other night.
 

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A couple of thoughts for things to check: the 8-pin connector on the junction box is tied to your headlight fuse and headlight relay. Trace the wiring and make sure there's not a problem with the relay. The other thing that occurs to me is that the reserve lighting device should have kicked in... (R/Y coming off the headlight, B/Y at the reserve unit). Check the leads on the unit and make sure they're solid. Sounds like it's definitely a wiring issue and not the bulb.
 

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Discussion Starter #3
I finally figured out that the headlight is tied to the ignition in some way. All lights except the headlight come on when the ignition is on. The headlight does not come on until the engine is cranked. Sometimes mine comes on sometimes it does not. Is there some type of switch that turns on the headlight when the bike is cranked? Electrical is not my strong suit.
 

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Search Goddess
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There is a diode/relay in the junction box that keeps your headlight off until the engine actually starts. this saves all of your battery juice for the initial start.
However when this diode/relay goes bad sometimes you are left without a headlight totally. There is a way to bypass it but you best make sure you have a maintenance free battery and it's charged because the headlight will come on as soon as the key is turned.

And the relay bypass instructions:

This can be bypassed to operate like an "other than US & Canada" VN750. (European models actually have a switch on the controls to turn the headlight on)
Look at the 8 pin connector going into the junction box. You will see that there are only 7 wires. Move the blue wire to the empty position and your headlight will come on when you turn the key on.
No more diodes, no more relay.
 

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Discussion Starter #5
Thanks for the advice Dianna. At this point, I am a little nervous about my charging system. I just bought a new maintenance-free battery but at 4000RPM, my volt/ohm meter reads only about 13.5 volts instead of the required 14.5. I wanted to know if the diode/relay in the junction box can be replaced? If not, until trace down the charging problem, I may have trouble cranking my bike with the headlight on constantly. I run a maintainer at night, but I worry about stopping for gas and having to restart on the way to work(about 33 miles).
 

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A solution to the headlight on is o buy a simple toggle switch and hook that onto the blue wire which is then on the bypass. You canswitch the light on and off as you please. The placement of the toggle is up to you and real easy to do. Good Luck.
 

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the headlight is trigered by the power from your alternator if your r/r is playing up it won't always come on. but if you fined yourself without headlight again justfire up get her rolling at about 15mph pull in the clutch kill the engine will the handle bar kill switch (the headlight will now come on) put switch back to run and let out the clutch to bump start the bike, the headlight should still be on.hope this helps.
p.s. do check your r/r/ and alternator outputs.
 

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Discussion Starter #8
EDALBRIS, thanks for the advice about the kill switch. Thar sounds fairly easy. I need some help with the R/R and alternator. Exactly where do they reside and how do I check them. Something is not right because at 4000RPM the output is 13.5 instead of 14.4 and I don't think my battery is charging fully.
 

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the r/r is mounted right under the battery cradle on the bottom.
there are two wiring looms that come out of the left hand engine casing go under the bevel box and the wing arm pivot and head up towards the battery, one of these is from the alternator (3 yellow wires ) unplug all three wires and check the readings out of each (the figures for what readings at what rpm you will find in the 'verses' section of this site).
on the r/r you will see a 6 pin plug(you might have to unbolt the r/r to get at it, there are two rows of three wires one row is all yellows(from the alternator) the middle wire in the other row is the power feed to the battery from the r/r, it is best to check the out put of this wire with it unpluged, for this i have made up five short male to female spade leads (about 4" long) so i can pull the whole plug out then link the other five terminals/wires back up using the leads so i can get my multimeter probe on the power feed terminal on the r/r. also check the yellow wires for continuity between here and were they join at the rear of the engine. hope this helps.
p.s. check out the 'verses' there is alot of usful info in there and they cover r/r and alternator testing quite well.
 

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oh And Use Some Penertrating Oil On The Bolts That Hold The R/r On As They Are Usualy Rusted In, And Are Likly To Snap Before They Undo
 

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If you are going to do any type of repair on the bike, I would recommend the Clymer's shop manual. It will answer many of your questions and has photos and drawings to explain things as well. It will also help you prevent inadvertant damage to the bike by telling you what not to do. The manual is well written and if you have any questions that the manual doesn't explain to your satisfaction, you then have the group here to back you up. It's only about 20 bucks or so online and is more than worth the small investment IMHO.
 

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To add to that: you can get the Vulcan service manual free via download off the TOC Manufacturing site. Between the two of 'em (Service and Clymer's), it's hard to go wrong; and if you do, as Niterider said, there's a whole group here to back you up.

Just some quick tips on testing the r/r and the stator: from your description of your charging (voltage at 4K rpm), definitely sounds like there's an issue with the r/r. Instead of pulling it out frmo underneath the battery box, though, some folks have just put a new r/r in at the relocation point (by the left frame side cover). Edalbris is spot-on, that those bolts under thebattery box are nearly impossible to get out. Just pull the connector, install the relo bracket, and put on a new r/r. Easiest solution, and the old r/r can just sit under there and be out of the way.

You want to test resistance across all three stator leads (all yellow). Between any two leads, I believe you should have a reading between .3-.5 ohms.
 

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Straight roads are evil
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A very likely cause is a low battery, which could be caused by a bad stator.

Basic info:
When the key is turned ON, a circuit in the junction box prevents power to flow to the headlight. That allows maximum power for the starter motor. Pushing the start button engages the circuit, when the starter motor button is released, the headlight is on.

If the engine then dies, the headlight is still on. Pressing the starter button engages another circuit, killing the headlight when the button is pressed, once again for maximum power to the starter.

If the battery is low, or the junction box faulty, the circuit might not engage, leaving the engine on but headlight off. Fully charging the battery should fix the problem; also inspect the stator to see if it's bad. (Instructions in the Verses, or the sevice manual.)

Good luck! Start with charging the battery, see how it goes from there.
 
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