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Headlight Wires?

TrailBoss

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Can somebody tell me which wires inside the headlight plug are:

1. 12v power (low beam)
2. 12v high beam
3. Ground?

I think they are white, blue, and black respectively but I can't get my multimeter probes in to verify.
 

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Fun4me

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According to the wiring diagram at the back of the service manual, 12v power to both is white/black; low beam is white; high beam is yellow/white; and ground is green.

Just curious, what are you trying to do? I've got a suggestion for connecting a USB charger that turns on & off with the key.
 
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TrailBoss

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According to the wiring diagram at the back of the service manual, 12v power to both is white/black; low beam is white; high beam is yellow/white; and ground is green.

Just curious, what are you trying to do? I've got a suggestion for connecting a USB charger that turns on & off with the key.
Excellent! I need to order a service manual.

I just mounted a set of fog lights and instead of using a switch I want to tie them directly to the high beam instead. I have the relay installed and everything up and running, I just needed to know which ones were the ground and high beam.
 

Fun4me

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Excellent! I need to order a service manual.

I just mounted a set of fog lights and instead of using a switch I want to tie them directly to the high beam instead. I have the relay installed and everything up and running, I just needed to know which ones were the ground and high beam.
Sounds like a great mod. I'm sure we'll see photos posted of the finished project.
 

Dogsbody

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That was my thought. Did wonder if there was an alternative I hadn’t considered.
 

Fun4me

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That was my thought. Did wonder if there was an alternative I hadn’t considered.
Here's how I connected my USB charger port so it turns on only when the ignition is on. Key off so no need to disconnect the battery. Removed headlight ring, disconnected the headlight using the small gray connector (not visible in the photo) and set it aside. Made a small cut in the electrical tape to easily access the black/yellow wire going to the larger black connector in the center of the photo. Used a blue size Posi-Tap connector to attach the red (positive) wire to the black/yellow wire. Used another Posi-Tap connector to attach the black (negative) wire to the green (ground) wire going to either of the turn signals, located in their separate two wire connectors. I chose the one on the right. The one on the left is also clearly visible in the photo. Reassemble and It's a simple, five minute job.

USB.jpg
 

TrailBoss

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@Fun4me, are you certain yellow/white is high beam? I tapped it as well as green, but I'm getting 0v. Yes, I am trying this with the motor running and the high beam switch on.
 

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Fun4me

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@Fun4me, are you certain yellow/white is high beam? I tapped it as well as green, but I'm getting 0v. Yes, I am trying this with the motor running and the high beam switch on.
TrailBoss, I've attached a scanned file of that section of the wiring diagram from the Service Manual. I'm sorry, but may have told you wrong. If you look at the bottom 'dimmer switch' section it shows white for low and yellow/white for high. However, at the 'headlight' section on the left it shows white for high and white/yellow for low. I'm truly sorry for causing confusion with bad info.
 

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TrailBoss

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I think my idea is a bust.

I checked White, White/Black, Blue, Yellow/White... The one that APPEARS to do what is needed is the white wire. It changes voltage based on the high beam switch. HOWEVER, the problem seems to be that even in the low beam position, the white wire is still putting out about 8v, and that's enough to trip my relay and turn on the lights. With high beam on it puts out 14.4v, which trips it as well, as expected.

My guess is since this is an LED headlight system they were able to take some liberties with threshold voltage that you normally wouldn't be able to do in an analog system. So 8v isn't enough to reach the LED threshold and turn the high beam on, but it won't work in my particular situation.

I think at this point I'm punting and I'm just going to get a handlebar mounted switch and be done with this. Unless we have some electrical engineers around here that might have some explanation to this electrical devilry!
 

TrailBoss

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TrailBoss, I've attached a scanned file of that section of the wiring diagram from the Service Manual. I'm sorry, but may have told you wrong. If you look at the bottom 'dimmer switch' section it shows white for low and yellow/white for high. However, at the 'headlight' section on the left it shows white for high and white/yellow for low. I'm truly sorry for causing confusion with bad info.
No harm at all. That's what forum are for, information, sometimes good, sometimes bad, but always helpful!
 

Fun4me

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I think my idea is a bust.

I checked White, White/Black, Blue, Yellow/White... The one that APPEARS to do what is needed is the white wire. It changes voltage based on the high beam switch. HOWEVER, the problem seems to be that even in the low beam position, the white wire is still putting out about 8v, and that's enough to trip my relay and turn on the lights. With high beam on it puts out 14.4v, which trips it as well, as expected.

My guess is since this is an LED headlight system they were able to take some liberties with threshold voltage that you normally wouldn't be able to do in an analog system. So 8v isn't enough to reach the LED threshold and turn the high beam on, but it won't work in my particular situation.

I think at this point I'm punting and I'm just going to get a handlebar mounted switch and be done with this. Unless we have some electrical engineers around here that might have some explanation to this electrical devilry!
Yeah, that's what I'd do too. Electrical stuff has always been FM (f--king magic) to me. Thought the wiring diagram would help but it still looks like a bowl of spaghetti. Good luck.
 

TrailBoss

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I *could* pull down the voltage with a resistor to below the pull-in voltage of the relay, which is *probably* around 8v if I had to guess. I wish I had a potentiometer handy... I could determine the pull-in voltage for the fog light relay, then calculate the resistor required to pull the voltage down to just below that. Heck, it just might work!

terminator.gif
 

timmmy todd

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Jan 15, 2021
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I Took volt meter to plug plug in head light with ignition on and still plugged together. stick probe in back side of plug till you find voltage with key on . I then striped positive wire. tined end with solder stuck it in to back side of plug like tester probe. taped it in place. put ground wire to horn mount. IT has been working well .shows running voltage. 400 miles so far .
 

Dogsbody

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Mar 17, 2021
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Fun4me, took the power from the Black/Yellow as you suggested. Seems that looking at the wiring diagram the power to the headlight is from the rectifier and not the battery direct so more likely to fluctuate with the rpm.
 

Fun4me

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O'Fallon, Illinois
Fun4me, took the power from the Black/Yellow as you suggested. Seems that looking at the wiring diagram the power to the headlight is from the rectifier and not the battery direct so more likely to fluctuate with the rpm.
Good to know. I'm only using it to charge my phone or GoPro so don't know if that will be an issue. RPMs will be fairly high most of the time which should be enough to keep them charged. I'll keep an eye on it and come up with a plan B if necessary.
 
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