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Discussion Starter #1
Hi. I'm having headlight issues similar to some on this forum. The headlight on my 1994 VN750 stopped working. There is no power at the headlight, and there is no failure indication on the dash. The harness plug at the Regulator/Rectifier was partially melted and the wires were corroded. A portion of the metal lip on the r/r terminal was burned away (probably not service affecting). I replaced the plug, the last 6" of the harness wires, and put on new metal clips. Still no light. I tested the R/R per the service manual and it test OK. The stator tests OK as well.

I'm about to begin testing light relay.

Any help you can lend will be greatly appreciated.

ThommyG
 

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When you tested the stator im assuming you have 1-3 Ohms resistance between the 3 leads and no resistance to ground. The voltage readings were about 50-70 VAC with the bike at 3000-4000 RPMS. With the wires burned up at the R/R connector is would seem to me something had shorted. maybe due to the corrosion.

One of the stator wires is spliced and goes to the junction box for the operation of the headlight relay. From what i see the R/R would have nothing to do with the operation of the headlight.

The headlight failure indicator on the dash means that the reserve lighting device has detected a headlight filiment burned out and it has switched to the good filiment.
 

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Discussion Starter #3
When you tested the stator im assuming you have 1-3 Ohms resistance between the 3 leads and no resistance to ground.
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Stator coil resistance: The service manual says .34-.52 ohms. I saw about .5;
Stator coil insulation: The service manual says infinite resistance to ground. That's what I got. (Otherwise the stator winding would be shorting out).

There was no indication of a headlight problem, and I guess that's probably OK because the bulb was OK. I'm beginning to think its the headlight relay.

Thank you for your response.
ThommyG
 

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Stator coil resistance: The service manual says .34-.52 ohms. I saw about .5;
Stator coil insulation: The service manual says infinite resistance to ground. That's what I got. (Otherwise the stator winding would be shorting out).

There was no indication of a headlight problem, and I guess that's probably OK because the bulb was OK. I'm beginning to think its the headlight relay.

Thank you for your response.
ThommyG
I think Ifixf18s "no resistance" statement was just a typo. His 1-3 ohms resistance specs probably come from our late, great "professor" Ron/lance328. I recall Ron saying stator resistance readings between the 3 yellow leads up to 2 ohms were ok. Your readings are well with in the service manual specs and seem to indicate the stator is ok.

If I read your OP correctly, the headlight failure indicator on the dash did not light up. I believe I am correct in saying that the indicator on the dash only lights up once when the filament burns out and Lighting Reserve Unit switches to the other filament. (My dash indicator light always has a dim glow, but is almost unnoticeable in daylight.) If you turn the key off and back on, the RLU does not switch to the good filament again when the engine starts.

You say there is no power to the headlight, so I assume you have opened the headlight bucket, unplugged the headlight and tested the harness connector contacts.

Have you tested the headlight bulb function itself with jumper wires or the like directly from a battery or a battery charger? Just trying to be thorough in understanding exactly what tests you have done.:)
 

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Discussion Starter #5 (Edited)
From this and other fora I found the headlight relay is problematic on Vulcan 750s. The easiest fix, as pointed out on this forum, is to bypass the headlight relay by moving the blue wire at the wiring harness plug to the vacant slot in same plug. That worked.
 

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JIC you issue has not been resolved this may help

I know it has been quite awhile since you posted this headlight issue but just in case it has not been resolved here is my 2bits:
I had a similar issue but not the melted wire part of it. I found that the root cause was a bad trace in the junction box so I got the handy dandy soldering gun and reconnected the trace. As for why this trace went bad I would have to guess that when I went to buy the bike the battery was weak and the bike would not start so seller jumped it and accidently stared a fireworks show after grounding the positive. (I got a discount for seeing that action) I am going to get a backup junction box because I am pretty sure the components took a good hit and will fail at some inconvenient time.
 

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I know it has been quite awhile since you posted this headlight issue but just in case it has not been resolved here is my 2bits:
I had a similar issue but not the melted wire part of it. I found that the root cause was a bad trace in the junction box so I got the handy dandy soldering gun and reconnected the trace. As for why this trace went bad I would have to guess that when I went to buy the bike the battery was weak and the bike would not start so seller jumped it and accidently stared a fireworks show after grounding the positive. (I got a discount for seeing that action) I am going to get a backup junction box because I am pretty sure the components took a good hit and will fail at some inconvenient time.
OK, I`m not much of an electronics guy, so please explain what a "trace" is, and why you call it that.
From the context I take that it is a wire, but what is a trace, and why/how does reverse polarity affect it?

Oh and BTW, welcome to the Vulcan madness. :smiley_th
 

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