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

Thread: Blue wire bypass - headlight relay mod Reply to Thread
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:

Register Now

In order to be able to post messages on the Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Once registered, your User Name"cannot be changed". We can make exceptions within 7 days, but after that, it is set in stone.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


  Additional Options
Miscellaneous Options

  Topic Review (Newest First)
10-26-2019 11:01 AM
Originally Posted by BannedAde View Post
What is the “reserve” lighting unit for?
And how do I check it’s working please?
As still baffled as to why I have power going to the blue wire from the headlight fuse, but no power at the light... 🤔
The reserve lighting unit will automatically switch from low beam to high beam if it detects a filament failure. Without you having to toggle the headlight switch. If there is any intention on going to an LED headlight, it could cause flickering because the LED bulbs do not consume as much power as the stock incandescent bulbs. It can be bypassed very simply by using a jumper across 2 pins on the connector. That mod can be easily found on here (with pics) by running a search on “RLU bypass”
10-26-2019 10:29 AM
BannedAde Thanks for your help Thorn btw 👍😁
10-26-2019 10:26 AM
BannedAde What is the “reserve” lighting unit for?
And how do I check it’s working please?
As still baffled as to why I have power going to the blue wire from the headlight fuse, but no power at the light... 🤔
10-26-2019 04:21 AM
Thorn Hi Ade,

After the standard blue wire mod, the headlight fuse will be unused, and the taillight fuse will provide power to the headlight.
Replacing the headlight relay requires desoldering the old component and soldering a new one back onto the circuit board. It is not a horrible procedure if you're comfortable soldering, if you can find the right component to buy.

Regarding the rest of your problems, I suggest starting a new thread specific to resolving the problems on your bike since it sounds like there's going to be a lot of investigation involved and we should try to keep the post count low on this "how-to" thread to keep things clear for future readers of the blue wire mod.
10-25-2019 04:36 PM
BannedAde Hi Guys (and Gals) 👋 I’m in England and have just joined. I’ve recently replaced my stator and rectifier and suddenly have the dreaded “Headlight not working” scenario. I think a mod was done to the bike before I got it (late last year) as the headlight used to come on with the ignition switch. I can’t see the “blue wire mod” at the fuse box end though and the connector where one would expect the power to come onward from the fuse is empty, so where does it go and is it really protecting the headlight circuit????☹️
My question is - is the headlight relay replaceable? And if so how? As this seems to me to be the obvious solution...
I’m no electrician, so please excuse me if the answer is staring me in the face!
Safe journeys all
06-06-2019 10:58 AM
Spockster The ground wires on this bike are black w/yellow stripe. Ground switching is the best way to go when it's possible, no chance of it shorting out. My voltmeter is switched on the ground side.

If you get the AGM battery, the headlight staying on should be no problem.
06-05-2019 07:11 PM
Ron Ryman
Originally Posted by Vulcan Rules View Post
For the Blue wire mod cons - Headlight stays on when key is turned on, which obviously takes power away from starting.

What I did was splice in a good quality mini toggle switch between the ground headlight wire inside the headlight cover, drilled a small hole in the lower head light cover to run the mini toggle switch through. The switch can then be off for starting, then easily turned on when warmed up and ready to ride. Very inexpensive easy fix to get full power for starting, after doing the Mod.
Can you explain this with wire colors and step by step instructions I did the blue wire mod and would like to install a switch?[emoji223]

Sent from my SM-J700T1 using Tapatalk
06-17-2018 10:32 PM
magicdave2 Got the RLU bypass done a few days back. It solved the flicker-y Headlight light on the dash! And, after the blue wire mod, the light comes on when the key turns, which is very nice. Also, the LED has a much better spread and is just brighter at night.

I also replaced my rear brake/running light with two LEDs. Changing these and the headlight to LED has really reduced the dim of lights at idle while the brake light is being activated like at a stop light.

There is a barely noticeable flicker with the new LEDs only at idle, but it's very minimal and I don't think I'm going to worry about it.

Thanks for the help guys!
06-17-2018 07:00 PM
warbike Did this, made going through the lights electric system much better. Plus I like it just coming on with the key and knowing the headlight is working right away.

Sent from my XT1585 using Tapatalk
06-14-2018 11:47 AM
Originally Posted by Vulcan Rules View Post
Hey that is a good idea if a stator goes out, pull the headlight fuse and just ride in the daytime. You can do the switch mod later if you decide to replace the stator. I would guess pulling the fuse would cut the power to everything related to the head light circuit. Will have to look at a good wiring diagram, the ones I've found so far for the vulcan are terrible, small, black and white, plus blurred out.
Pretty sure its the LAW to run a headlight on your Motorcycle here in sunny Florida.So......my Stator pooped out so tried the "Battery tender" thing,was OK but really tough to figure when that battery would die...then leave you sitting/walking.Not a enjoyable way to ride!!
This thread has more than 10 replies. Click here to review the whole thread.

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

For the best viewing experience please update your browser to Google Chrome