HOW TO: Install a headlight modulator

Have you ever seen those motorcycles coming at you with those headlight modulators? The pulsating headlight makes them very noticeable to other motorists. Unfortunately, these units can be rather expensive. After doing some research, I've come up with an inexpensive way of replicating these headlight modulators.

We'll need a couple of components for our project. We're going to use a Grote electronic flasher, part number 44530, to handle the headlight pulsation. We'll also be using a 30 Amp double-pole relay, Standard Motor Products part number RY48 (or NAPA PN# AR204).



Other parts include a little bit of wire (14 or 16 gage, less than a foot in length) and several insulated female spade terminals. As far as tools are concerned, you'll need a philips screwdriver, a jeweler's flathead screwdriver (about 1/8" wide) and a pair of wire cutters/crimpers.

I've come up with two different versions of how to hook this circuit up. One way has the headlight's high beam oscillating when the headlight dimmer switch is flipped to high beam. We'll call this Option One. The other has the headlight's high beam oscillating when the headlight dimmer switch is flipped to low beam. We'll call this Option Two.

Before we begin, let's familiarize ourselves with the connections on both the relay and the flasher unit.

The Relay



The relay will have five spade terminals sticking out of it. Two of the five terminals are hooked to an electromagnetic coil inside the relay and they are marked 85 and 86. Terminal 85 is the power-in terminal and terminal 86 will be hooked to ground completing the circuit. The other three terminals (terminals 30, 87, and 87a) are for a double-pole switch. The term "double-pole switch" tells us that the switch has the possibility of sending power down one of two legs depending on its state. Our relay has two states: energized or not. The "not energized" state will have terminals 30 and 87a connected in a normally closed (nc) position, allowing power to flow across them. Terminals 30 and 87 are said to be normally open (no) in this state, i.e. no power will flow across those terminals. The "energized" state is when the coil has been powered up on terminal 85 and the relay's electromagnetic coil pulls the switch closed across terminals 30 and 87. Now terminal 87 is closed and terminal 87a is open. As soon as power is removed from terminal 85, a spring pushes the switch back to its "normal" state, closing across terminals 30 and 87a. Notice that terminal 30 is a common terminal to both states. Therefore, terminal 30 is usually referred to as the "common".

The Flasher



When you look at the electronic flasher, you will see an 'X' and an 'L' stamped on the unit. Power coming into the unit should be hooked to the 'X' terminal and the headlight high beam should be hooked to the 'L' terminal.

We will also need to adjust the flasher's rate of oscillation. You will need to carefully remove the plastic cover from the electronic flasher unit by gently prying out on the retainer clips on either side of the cover. Once the cover is removed, you will see a pot on the circuit board next to the capacitor. The pot has a small square hole in it that is adjustable. Using a small screwdriver, turn it clockwise to increase the flash rate or counterclockwise to decrease it.



I recommend doing this before building your harness as things get pretty tight afterwards. A couple of jumper wires will work to temporarily hook up the headlight and flasher unit. You'll need to hook one jumper wire to the yellow wire coming from the dimmer switch to the 'X' terminal on the flasher. Then hook another jumper wire to the 'L' terminal on the flasher unit to the yellow wire of the headlight harness. Lastly, you'll need another jumper wire hooked to the black wire of the headlight harness to ground to complete the circuit.

After securing the headlight so it doesn't fall and break, start the bike and turn on the high beam. Slowly turn the pot until the highbeam oscillates on and off at a decent rate. If you turn it too much, the high beam will not fully light and will diminish the effect. Once you have it set to where you like it, replace the cover. (WARNING: Be carefull where you grab the flasher's printed circuit board. The capacitor can give you a nasty jolt if you touch its terminials.)

Here are the steps...
1. Remove the headlight from the headlight bucket by removing the two screws from the bucket. They are located at the 4 o'clock and 8 o'clock positions.
2. Unplug the headlight from the wiring harness and set it aside for now.
3. Unplug the headlight harness from the dimmer switch wiring harness.
4. See the instructions under the flasher unit section for adjusting the flasher frequency. Adjust flasher unit.



5. Cut the headlight harness approximately in half.
6. Remove any plastic wire protector tubes from the harness and discard.
7. Determine which option you will be installing on your bike. Option One will preserve the low beam, while Option Two will preserve the high beam.
8. Go to that section to complete the install.

Option One (Preserves Low Beam)



Here's the wiring diagram I've come up with for oscillating the high beam when the headlight dimmer switch is in the 'High' position. This is how it works: power flows to the normally closed side of the relay contacts, terminal 87a, through to terminal 30. From there, power continues on to the low beam filament of the headlight. At the same time, power flows to the flasher unit, then on to the high beam filament of the headlight. The flasher unit causes the high beam filament to oscillate on and off rapidly.

To disable the headlight modualtion feature, flip the headlight dimmer switch to the 'Low' position. Power then flows to the relay's coil terminal 85 energizing it (terminal 86 being grounded). At that point, the switch inside the relay closes across terminals 87 and 30. Power then flows from terminal 87 through 30 out to the low beam filament.



9. Using your wire strippers, strip the insulation off all the headlight wiring harness wire ends.
10. Twist together both the bare black wire ends and crimp on an insulated female spade terminal.
11. Plug this newly crimped female spade terminal onto the relay's terminal 86.
12. Twist together the bare green wire end coming from the headlight wiring harness's dimmer switch circuit (white plug-end) and a short piece of new wire (stripped of course) and crimp on an insulated female spade terminal.
13. Plug this newly crimped female spade terminal onto the relay's terminal 87.
14. Crimp on an insulated female spade terminal on this new wire.
15. Plug this newly crimped female spade terminal onto the relay's terminal 85.
16. Crimp on an insulated female spade terminal on the bare green wire coming from the headlight wiring harness's headlight end (black plug-end).
17. Plug this newly crimped female spade terminal onto the relay's terminal 30.
18. Twist together the bare yellow wire end coming from the headlight wiring harness's dimmer switch circuit (white plug-end) and a short piece of new wire and crimp on an insulated female spade terminal.
19. Plug this newly crimped female spade terminal onto the relay's terminal 87a.
20. Crimp on an insulated female spade terminal on this new wire.
21. Plug this newly crimped female spade terminal onto the flasher's terminal 'X'.
22. Crimp on an insulated female spade terminal on the bare yellow wire coming from the headlight wiring harness's headlight end (black plug-end).
23. Plug this newly crimped female spade terminal onto the flasher's terminal 'L'.
24. Go to step 25.

Option Two (Preserves High Beam)



On the low beam side, power flows in from the dimmer switch to the low beam filament and to the flasher unit. From the flasher, it flows threw the normally closed (terminals 87a and 30) relay on to the high beam filament. The flasher causes the high beam filament to strobe.

When the dimmer is flipped to high, the power flows into the coil of the relay (terminal 85) which pulls the contacts closed across terminals 87 and 30. This allows the power to flow from the high beam circuit threw to the high beam filament. Since there's no flasher involved, it remains constant, i.e. a normal high beam.



9. Using your wire strippers, strip the insulation off all the headlight wiring harness wire ends.
10. Twist together both the bare black wire ends and crimp on an insulated female spade terminal.
11. Plug this newly crimped female spade terminal onto the relay's terminal 86.
12. Twist together the bare yellow wire end coming from the headlight wiring harness's dimmer switch circuit (white plug-end) and a short piece of new wire (stripped of course) and crimp on an insulated female spade terminal.
13. Plug this newly crimped female spade terminal onto the relay's terminal 85.
14. Crimp on an insulated female spade terminal on this new wire.
15. Plug this newly crimped female spade terminal onto the relay's terminal 87.
16. Crimp on an insulated female spade terminal on the bare yellow wire coming from the headlight wiring harness's headlight end (black plug-end).
17. Plug this newly crimped female spade terminal onto the relay's terminal 30.
18. Twist together the bare green wire end coming from the headlight wiring harness's dimmer switch circuit (white plug-end) and the bare green wire coming from the headlight wiring harness's headlight end (black plug-end) and crimp on an insulated female spade terminal.
19. Plug this newly crimped female spade terminal onto the flasher's terminal 'X'.
20. Crimp on an insulated female spade terminal on a short piece of new wire.
21. Plug this newly crimped female spade terminal onto the flasher's terminal 'L'.
22. Crimp on an insulated female spade terminal on this new wire.
23. Plug this newly crimped female spade terminal onto the relay's terminal 87a.
24. Go to step 25.

Finishing Up
25. Carefully reposition the existing wires in the headlight bucket so that you have room for the relay and the flasher unit.
26. Plug the headlight wiring harness into the headlight dimmer switch harness (white plug-end).
27. Plug the headlight into headlight harness.
28. Reinstall the headlight, making sure not to damage the wires, connections, or components inside the headlight bucket.
29. Reinstall the headlight bezel retaining screws.

That's it! You're done.

In closing, here's a little video of the working prototype on my bike. In the video, you'll see me switching the headlight dimmer switch from 'Low' to 'High'. Note the strobing of the headlight after I've flipped the switch.

[video=352,285]http://home.att.net/~d-n-asoftware/video/headlight_modulator.mpg[/video]

I want to thank all those who helped in creating this How-To by submitting suggestions. Without your input, it would not have turned out nearly as complete. I must warn you, this modification isn't strictly "legal". So, use at your own risk.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

no more High beam? That's the only way I can see at night.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

Yeah, I agree with PghXJ...high beam is the only way to see - especially on the highways that are not lit, like most of them in Chilly Beach. Could this not be re-done to allow it to pulse high beam on the low beam setting, preserving high beam? Needs a better mind than mine. My brain turns to puddin' thinking about electrics.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

I like the idea of being seen more easily. I usually run with my highbeams all the time. I am sure that is iritating to others, but I'm more concerned for my visibility than their comfort. I also have the old lamp so I am definately not blinding anyone to a level of creating danger from a blind motorist. If I were to try to set this up, what would be the response from law enforcement? It seems that IN the city, they have greater concerns than tight traffic enforcement, but once out of the city-shooting limits, it would appear that law enforcement has a lot less to do other than hassel situations they aren't familiar with. Is this legal everwhere? How could I convey that it is a legal modification also?

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

My thoughts went to using it on the braking system instead of the headlight.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

I have a friend who swears by 100% highbeams all the time. He has a GSX-R1000, new, super bright - figure the headlight of a bike is plenty high to be in my direct view, either in front or in my rearview when Im driving a car (93 Probe GT - nice and low).
Not just his, but plenty of older bikes on the road running full time highbeams. At least I can turn my rear view mirror away. Now I cant see anyone following.
If I'm being blinded headon and a critter or kid runs out, who knows which way I'll swerve since I may not be able to see everything very well.

A dude I know with a lifted Ranger wired his headlights and offroad lights ot always be on. No lowbeams. His under bumper lights were nasty to cars he was following. His standard headlights and rollbar lights were both quite bothersome when he was behind my suburban! (he had 4 rear facing offroad lights too, on 100%)
Granted he was on WAY overkill - (to get slow drivers out of his way) but he finally got stopped when he pulled up on the rear bumper of a county cop. Fined and made to fix the headlights, and

Just recently I noticed a Harley-Davidson cruiser a ways behind me and I thought it was a cop bike due to the flashing lights. It was 4 or 5pm, so not nearly dusk. I happend to be stopping for fuel and watched as he passed. His head light want flashing, it was the two driving lights. His lights werent blinding at all, and there were noticable. If he had been closer when I first saw, I may have pulled over to let him by.

The Wisconsin motorcycle handbook states:
Use Your High Beam: Get all the light you can. Use your high beam whenever you are not following or meeting a car. Be visible, wear reflective materials when riding at night.

I was going to add another comment about police and thier spot-lights blinding every oncoming vehicle when they have a victim pulled over. but Ill stop here.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

According to this page, this modification isn't strictly "legal" since you'd loose the functionality of your highbeam if the flasher failed (I think... maybe not). But it doesn't have a nighttime override, so that makes it illegal, too. Again, use at your own risk!

While examining my original modulator circuit, I discovered a flaw in the way I had it hooked up.



To correct this I've had to replace the Grote relay with a Standard Motor Products relay (PN# RY48). What was happening was that once the circuit was energized--or latched--you couldn't shut it off unless you shut the bike off. To correct this, I had to rearrange the components and change the relay to a double-pole.

Here's the new wiring diagram...



For those in the crowd who wanted the low beam to oscillate instead of the highbeam, all you need to do is swap the terminals (green and yellow) coming into the headlight bucket from the headlight dimmer switch. I will tell you now that I original set this up to modulate the low beam, but discovered the brightness of the highbeam made the lowbeam's flashing almost unnoticeable. You may have better luck with your headlight... you'll have to just try it and see.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

I’ve wired up and installed the components as per the second version of my wiring diagram. Success! The change in relay solved the latching problem. I'll road-test it today on the way in to work and back home tonight.

I'm giving more thought to those who've requested that the high beam be left constant while the dimmer switch is in the 'High' position, but oscillates the highbeam while in the 'Low' position. I'm going to look to see if that's possible with these components. If it is, I'll post an appropriate schematic.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

Dude, this is just too neat! Don, you have earned my appreciation, your next brew is on me (provided your in town and have set the keys aside).

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

Gamuru, you are correct in the interpretation of what I was asking. Thanks and good luck!

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

Robert, if I ever venture that far South, I'll take you up on that offer.

PSteele, et al., I've got it! It took a couple of tries, but I figured out the circuit for what you asked for...



A brief description: On the low beam side, power flows in from the dimmer switch to the low beam filament and to the flasher unit. From the flasher, it flows threw the normally closed (terminals 87a and 30) relay on to the high beam filament. The flasher causes the high beam filament to strobe. When the dimmer is flipped to high, the power flows in to the coil of the relay (terminal 85) which pulls the contacts closed across terminals 87 and 30. This allows the power to flow from the high beam circuit threw to the high beam filament. Since there's no flasher involved, it remains constant, i.e. a normal high beam.

What a brain-bender! Now, to finish this How-To...

(Oops! I almost forgot. My road test was a success. I didn't have a lick of trouble with the headlight modulator circuit. I had to shut it off before I made it home as I ran into the meanest looking black rain cloud you've ever seen! And it was dark.8O)

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

Just curious but how much of a difficulty level would you give the low beam to strobe opporation?
I dont get out to the auto parts store too often but a guess as to the approx cost?
Sounds like something I might do this off-season.
I like wires better than carbs.
I need to do the fuse box replacment you made me think of too.
Gamuru you have my vote for How To Guy of the Year, thanks.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

You ARE submitting this to the maintainers of the XJCDs, yes?

(staring intently at Gamuru)

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

For the novice? Fairly difficult.
For the pro? Easy-squeezy.
And for the rest of us? If you can change the fusebox, you can do this.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

now that is useful to me. Thanks for returning high beam functionality.

 

Re: HOW TO: Install a headlight modulator (DRAFT VERSION)

Gamuru: brain-bender though it was, this is a great mod! Kudos to you and your bent noodle and thanks for contributing to a bunch of strangers that are only connected by an attachment to old bikes and smelling of gas all the time. You'd think we'd have something better to do, but so far this cranky old bike has been a highlight for me. Thanks again.

 

PSteele, you're welcome! It was a challenge to work this out and I enjoyed it.

I've got good news for everyone: the How-To is officially done! Have fun with it.

 

I'm enjoying the detailed drawings and the movie.

I can't Post another Pic because my 5 Bites are used-up.

This is going to be my Winter Project. I know I'm going to whacked by that Capacitor.

 

This is a two-week update: so far, so good. I haven't has a lick of trouble with the circuit. The relay and flasher are holding up real nice. I have noticed that the flasher takes a minute or two to "warm up" on cold mornings. But, once it does, she's just a blinking away.

One day last week (I don't remember which), I pulled up behind one of our local cops at a stoplight on my way to work. There I was, headlight blinking away in his rearview mirror. I thought "Well, here's the acid test." I waited and waited for something to happen: the light turned green and we pulled away. Good to go!

One downside to running a headlight modulator is that people tend to slow down when they see flashing lights. So, if you're in a hurry, it could be problematic to leave it on.

All and all, I've been pretty happy with how this project has turned out.

 

You know Gamuru, I have found that cops that really care about vehicular safety understand what the needs of bikers are. They know that we are simply trying to be seen and welcome small variences like this one. These guys have probably scraped up a few of our lot that have not been seen and would rather deal with a headlight modulator** than a broken biker. I will get this done over the winter!

**Kind of sounds like Marvin the Martian - "What do you thing of my new XJ650J Super Mega Bright Headlight Modula-Tor? Isn't it Wonderful? Hmmm?"