Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums - Reply to Topic
Where does this wire go?
Includes Electrical mods, Lights, Stator,
Rectifier, Diagrams, etc

Thread: Headlight cut off Reply to Thread
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  Topic Review (Newest First)
11-20-2007 08:31 PM
EQPlayer 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.
11-20-2007 07:59 AM
Crobins365 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.
11-19-2007 11:42 PM
Sky Rider 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.
11-19-2007 06:19 PM
EDALBRIS 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
11-19-2007 06:14 PM
EDALBRIS 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.
11-19-2007 12:10 PM
lbcole0915 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.
11-17-2007 02:15 PM
EDALBRIS 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.
11-16-2007 05:30 PM
Redskinner 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.
11-16-2007 02:52 PM
lbcole0915 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).
11-16-2007 11:00 AM
Dianna 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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