Kawasaki VN750 Forum banner

Blue wire bypass - headlight relay mod

32503 Views 57 Replies 24 Participants Last post by  Mikeee15
This guide bypasses the headlight relay, lighting your headlight when you turn the key, instead of when the engine turns.

Don't ask me about the pros/cons of this; I'm sure it will be discussed.

Video detailing the procedure at https://www.youtube.com/watch?v=C1_1MTfiJb8

On the left side of the bike remove the side cover. Unscrew the bottom screw and pull the side cover off. If you are sitting on the side of the bike, facing the side cover, pull directly toward you.

You will see a Palm sized black box with two connectors coming out the right side of the box. One is a smaller ten pin, one is an 8 pin.


Don't make the mistake I made - don't touch the ten pin connector. I pulled the blue wire from the 10 pin and moved it to the 8 pin. This is WRONG.

Pull out the 8 pin connector.


There is a blue wire. Pull the blue wire out of its spot (or push it from the front of the connector to reduce stress on the wires) and move it to the empty spot on the same connector.


If the spade connector pushes out as you push the connector in, just connect the plug, then push the spade connector into the empty spot to secure it.

Operation complete.
See less See more
1 - 20 of 58 Posts
Thanks, much appreciated! A reasonably easy mod to do, but having pictures to look at definitely works better for me to understand what is to be done.
Well done - a great detailed write up ...with pics !

My headlight's bright light didn't work so I bought a new bulb. This didn't fix the problem.
I figured I had nothing to lose by switching this blue wire to bypass the headlight relay.
This fixed it. Bright light now works.

Glad it's still of use
  • Like
Reactions: 1
Based on the diagram on page 15-36 in the manual, this bypasses the headlight fuse as well. May want to seriously consider adding an in-line fuse to protect things.
Based on the diagram on page 15-36 in the manual, this bypasses the headlight fuse as well. May want to seriously consider adding an in-line fuse to protect things.
Actually if you see the schematic on page 15-50 for the junction box 8P connector, all you are doing here is removing the output from pin 8 and moving to pin 7. All that does is to take the headlight relay out of the circuit, the 10A headlight fuse (24 on the diagram) is still in the path. And you can verify that it is, by pulling the fuse after doing the repair, and seeing that the headlight will stop working.

This is a great mod, and can't beat the price !
Based on the diagram on page 15-36 in the manual, this bypasses the headlight fuse as well. May want to seriously consider adding an in-line fuse to protect things.
It actually moves it to a pin that is protected by the TAIL fuse, also 10 amps, so the headlight is still completely protected. You can even move the 'dash' lights (red/blue wire) to the originally empty spot (pin 17, tail-light fuse protected), and move the headlight (blue) to where the red/blue wire was. That gives you all the benefits of the mod while keeping the headlight on the headlight fuse for OCD people.

Crowley said the pros and cons would surely be discussed, but nobody discussed! Here's my take on it:

1. Protects against a dead headlight due to headlight relay failure.
2. Your headlight comes on as soon as you turn the ignition to 'on'.
3. No wires cut means this mod is completely reversible.

1. Since the headlight will come on when you turn the ignition to 'on', it lowers the available voltage to the starter motor.

I'm also going to recommend an additional step to the mod:
Remove the smaller, ten pin molex connector from the junction box. Using a small screwdriver, release the retaining pin on the yellow wire's blade connector (pin 9), which should be the second wire up on the back row.
Cover the blade connector in shrink wrap and heat it until securely insulated.
Use a small zip tie to gently but firmly secure this wire to the bundle of yellow stator wires that go to the rectifier/regulator so it doesn't wander somewhere it shouldn't.​

Additional pros:
4. Protects your stator from burning out if the headlight relay coil shorts out. (the safer the better)
5. Protects the starter relay (the one outside the junction box) from the constant unregulated voltage pulses it usually gets from the stator.
See less See more
  • Like
Reactions: 3
Thanks for clearing that up. That's great information!
Easy Fix for Blue wire mod cons

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.
Relay no fuse ?

Ty for the headlight switch info, that is a great idea and that is what I am going to do. Knew I was going to put a switch on just didnt know where.

Question, my stator is out, and I have been riding the bike all summer np, just keeping it on battery tender when not riding it. I just recently joined here and started getting familiar with the Vulcan elec system. I just found out the headlight has its own fuse, I should of thought of that way earlier, lol. So I pulled the fuse, the cops here dont care and I don't ride at night.

So, my question is, if the headlight fuse is pulled, the headlight relay is disabled and the headlight will draw 0 juice right ? Sounds like a stupid question, the headlight is off, so its draws no juice right? But I am just making sure there is no need for me to do the headlight mod if I am just going to leave the fuse pulled.

With the headlight fuse pulled and the biggest deep cycle gel battery I can fit in the hole, I bet I can ride a long time with no stator.
See less See more
the headlight relay itself will still draw power, however, its a small amount.

the headlight (low beam) is 55w if I recall.. disconnecting it will increase the time for battery to die.. but.... the tail/brake lights are a big draw as well.. I think each bulb draws about 15w? and there are 2 of them. Also the turn signals and running lights (front only) draw about 10w each, more in front if flashing.

unless you have replaced them with led's, you still have a considerable amount of draw from lighting.
  • Like
Reactions: 1
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.
The headlight fuse also powers forward running lights and all instrument lights (spedometer lights, fuel meter light, tach lights).

I have a wiring diagram linked in my signature that has clearly labelled wires plus some design notes. Still under construction, but always improving. Check back for the most recent version when you need.
I've got a quick question regarding the blue wire mod.

I bought an OPT-7 LED headlight bulb for my 750.

I did the blue wire mod and the LED lights right up when the key goes on. No flickering at low RPMS. It seems to be running at full brightness.

The odd part is when I'm riding and coming to a stop or accelerating from a stop the HEADLIGHT indicator light flickers on and off. It goes off when I pull in the clutch.

It doesn't seem to be causing any trouble or anything to not work right but it's irritating.

Any ideas??? Thanks!
Check out the Reserve Lighting Unit Bypass mod.
Hi Thorn,

I thought by doing the blue wire mod, I was bypassing the RLU. Is it only bypassing the headlight relay?

1 - 20 of 58 Posts