Headlight modulators were made legal in the US and Canada when daytime running lights became common on automobiles. Up until then, motorcycles had an added advantage to stick out in traffic: their headlights were on in daytime. With the advent of daytime running lights on cars, motorcycles once again blended into traffic. Headlight modulators restore that advantage.
Do they work? You bet they do! I myself have found that every time I see a motorcycle with a headlight modulator, it catches my eye instantly, drawing my attention to it. I have been riding with one for years, and have had lost count of the number of times people have come up to me and said, "hey, your headlight's flashing." The fact that they have noticed this, says to me that it's working - they're seeing me!
Disadvantages? Some people will claim that auto drivers will see your flashing headlight as a signal to "go ahead and turn left in front of me." I personally have NEVER had this type of thing happen - the steady, constant flashing is completely unlike a quick flick of the lights normally used to signal someone to "go ahead."
The main disadvantage is on highways. Riding a big motorcycle such as a Goldwing (and in my case, a big WHITE motorcycle), with a big fairing, antennae sticking up back and a flashing headlight tends to say "POLICE" to people when you come up behind them, and they will slow to the speed limit. Sometimes this is an advantage, as they will then pull out of their lane to let you pass.
I have installed three headlight modulators in three different bikes, and in every case I have used the Kisan PathBlazer. It is a little bit more expensive than some modulators, but they are tiny, simple to install, and are built extremely well - overengineered. They can be easily uninstalled, and can be controlled simply.
The PathBlazer functions on the high-beam circuit. When you switch your headlight to low-beam, the modulator is completely disconnected, and your headlight functions normally on low beam. When you switch to high-beam, the PathBlazer is engaged, and begins to modulate the high-beam filament in your headlight. This is great - you end up using your low-beam mostly at night, and your high beam mostly during the day, which means your headlights tend to last longer before burning out. If you want to turn the modulator off, like when you're in a group of motorcycles, and don't want to constantly flash the guy in front of you, just switching to your low beams disables the modulator.
When it gets dark out, a photocell detects this and disables the headlight modulator automatically, so that your high beam functions normally. All headlight modulators must have this feature by law. More on headlight modulators and the law at the end of this article. For now, let's get to the install!
1. Raise the windshield adjuster levers on either side to the up position.
2. Start to peel the rubber lip away from the mirror cover, beginning at the back and working upward.
3. Continue peeling the rubber lip away from the plastic mirror cover all the way around until it is completely detached. Take note that at the bottom rear, the rubber must be pulled toward the rear of the bike in order to detach it - this should be done after all of the rest of the rubber has been detached.
4. Gently pull the bottom of the mirror cover to unclip it from the fairing.
5. While holding the rubber back, pull the mirror cover free of the fairing, and let it drop down.
6. Expose and remove the two screws holding the chrome windshield trim in place (as shown). On 1994 and earlier Goldwings, remove the two screws holding the black plastic trim (below the windshield trim) in place and remove the black plastic trim.
7. Remove the two screws holding the windshield trim.
8. Slide the windshield trim to the right to unhook the lower tabs, then lift it away from the windshield.
9. Remove the screw holding the turn signal assembly in the fairing. It's not necessary to remove the turn signals, but it makes it a lot easier to maneuver the headlight in and out, and I recommend you do so.
10. Gently remove the turn signal from the fairing. There is enough wire behind it that you can let it dangle down if need be. Remove the other turn signal the same way.
11. Remove the two screws fastening the grill below the headlight.
12. Remove the grill from below the headlight.
13. Using a 10mm socket, remove the two bolts holding the top of the headlight. On later model GL1500's, these bolts also hold the bracket in place that fastens the bottom end of the windshield trim - pull this bracket away when you remove the bolts.
14. Using a 10mm socket, remove the two bolts holding the bottom of the headlight. Careful - these are the only things left holding the headlight in place! Use your hand to hold the headlight in the fairing as you remove the last bolt. Note that the bolts have a threaded hole tapped in their heads - these are where the screws fasten for the lower trim.
15. Gently pull the headlight away from the fairing. It will still be fastened by the wire in behind.
16. At this point, you will hear pieces falling down behind the headlight. Don't panic - there are four metal spacers that go into the holes in the fairing where the headlight bolts fasten. They will fall out. You can see one of them here.
17. Here is an example of where the upper spacers fit in the fairing. Collect the four spacers for now and put them aside.
18. Find the wiring connector on the back of the headlight, and press down on the locking tab on the connector.
19. Gently pull the connector apart. This will free the headlight so that it can be remove from the fairing.
20. Now that the headlight is removed, you can see where the lower spacers fit into the fairing. Remember to collect them now so they don't get lost! Reinstalling the headlight without them will result in a mis-aimed headlight.
21. As mentioned, the modulator that I use is the Kisan PathBlazer. For the GL1500, I use the 150GW model.
22. The modulator itself is tiny - it contains a microprocessor with memory, the ambient light detection circuitry, and the high-power light controlling circuitry. It is designed so that if the controller fails, it fails shorted, meaning the headlight will turn on. It will never fail in a way that you are left in the dark.
23. Unscrew the clamp holding the connector to the back of the headlight and pull the connector free.
24. Insert the female tabs of the headlight modulator into the headlight connector and put the headlight assembly aside (on something soft) for now.
25. The modulator's light photocell needs to have a clear view of the sky. I've tried several different places such as zip-tying it to cables, but without fail, the best place for it is on the dashboard. Due to the limited amount of room between the windshield and the dashboard, that means the windshield has to come off - but don't worry, it's a simple task! Start removing the screws and setting plates (the metal ovals) from the windshield. Start with the outer two screws, then the inner two screws. Note that the two outer setting plates (the two closest to the mirrors) are larger than the other three - make sure you keep them separate.
26. Next, while supporting the top of the windshield, remove the center screw, then lift the windshield up and away from the fairing.
27. Start by drilling a small pilot hole at the spot you want to install the photocell. The place I show here is a good spot, away from the speaker and any important components.
28. Once the small pilot hole is drilled, drill the larger hole required by the sensor. The PathBlazer instructions say to drill a 10mm (25/64") hole, but I found that this was too small - I had to go to a 13/32" drill bit in order to get it to fit.
29. Insert the connector end of the photocell into your hole, and feed it down inside.
30. Pull the wire from below the fairing through the hole at the back of the headlight area.
31. Insert the split collar around the wire of the photocell.
32. Slide the collar up to the top of the photocell.
33. Insert the photocell into your hole, and rock it back and forth to seat it in place.
34. Push the photocell all the way into the hole until the collar is flush with the dash. I think I will eventually paint the outside of the photocell bezel a flat black to match the dash - however the inside should be left shiny, to help reflect the daylight onto the photocell.
35. Lift the windshield into place, make it approximately level, then insert the center setting plate and screw to hold it in place.
36. Check to make sure the windshield is level again, then begin inserting the remaining setting plates and screws. Ensure the larger setting plates go into the outermost slots in the windshield.
37. As you can see, the photocell fits nicely under the windshield - there's nowhere near enough room to fit it in there with the windshield in place.
38. Plug the photocell wire into the back of the modulator, and ensure the lock clicks into place.
39. The modulator comes with a zip tie intended to fasten the photocell to existing cables if desired. I instead used it to gather and tidy the excess photocell wire behind the headlight. Don't let it drape down loose into the hole behind the headlight, where it could get pinched by the forks as the steering is moved.
40. Postition the headlight assembly near the fairing, and plug the wiring harness connector into the male tab side of the modulator as shown.
41. Once installed, the modulator should appear as shown. Now you can see why it is easy to uninstall this unit if desired.
42. Insert the four headlight mounting spacers into their upper and lower holes in the fairing as shown.
43. Tuck the wiring neatly behind the headlight, and gently push the headlight into place, so as to not dislodge the spacers. You will have to push the headlight and hold it in place against the spring tension of the headlight adjuster.
44. Insert and tighten the lower headlight bolts with a 10mm socket. Remember these bolts are the ones with the tapped screw holes in their heads.
45. Insert and tighten the upper headlight bolts with a 10mm socket. Remember to install the windshield trim bracket as well if your GL1500 uses one.
46. Now is the time to test things before buttoning everything back up. Turn the ignition to ON, and check that your headlight comes on normally. I use LEDs for my position lights, which is why they have a bluish tinge in this picture (I got sick of replacing burned out light bulbs).
47. Next, switch your high beams on. Assuming you are working inside a garage, your headlight will NOT start to modulate, it will simply switch the high beam on.
48. To test the modulator, take a bright flashlight and shine it directly on the photocell. The headlight should begin modulating instantly. Take the flashlight away, and it should stop.
49. Replace the trim below the headlight and screw it in place.
50. Replace the turn signals and screw them into place. Be careful not to over-torque the screw, as the plastic of the turn signal will crack.
51. Engage the fairing tabs in the slots in the windshield fairing, and slide the windshield fairing to the left to lock it in place.
52. Replace and tighten the screws holding the windshield fairing in place. If working on a 94 or earlier GL1500, replace the black plastic trim and the two screws holding it in place.
53. Holding the rubber back on each mirror, slide each mirror cover back into place.
54. Once in place, gently push each of the mirror cover clips until it latches onto the fairing.
55. Hook the rubber over the rear of the mirror cover, then work the lip around the circumference.
56. Once the rubber lip is around the circumference, push the locking tabs into their slots.
57. Lower the windshield locking levers into their locked positions.
58. The Kisan PathBlazer comes preset to the factory to automatically turn the modulator off when it gets to a certain darkness level. You can adjust this to your personal preference if desired (within limits). To do so, go outside in the evening, at the time of day at which the ambient light is at the level at which you wish the modulator to STOP modulating. Switch to low-beam. Turn the motorcycle off, wait a few seconds, then turn the keyswitch to ON, and immediately flick the high beam switch quickly three times - starting on low, you should flick it LOW-HIGH-LOW-HIGH-LOW-HIGH (leaving it in high) within two seconds. If done correctly, the modulator will flash the headlight FOUR times. This indicates that the modulator has memorized the current light level as the "switch point," and will use that from now on.
If you receive eight flashes instead of four, you have either not flicked the switch fast enough, or the ambient light level is below the limit at which the unit will allow you to set the switch point.
Is this thing legal?
In one word, yes. Federal law in both Canada and the US states that headlight modulators on motorcycles are legal. Federal law trumps state, local, or any other law.
But the police in my town says they're not legal!
They're wrong. Federal law is binding, making any local ordinance illegal and unenforceable. For this reason, I suggest you print out a copy of the DOT (in Canada, Transport Canada) regulations and keep it in your bike. This way you can show it to any misinformed law enforcement officer who may pull you over for having a "flashing headlight." You can find a small file containing the regulations (also reprinted below) that is perfect for printing in the Manuals section - look for "Motorcycle Headlight Modulator Regulations - USA and Canada".
Headlight Modulator regulations (USA)
This Federal law supersedes all state laws and makes motorcycle headlight modulators legal in all 50 states. FMVSS 108 (Federal Motor Vehicle Safety Standards) (49 CFR Part 571.108 S7.9.4) allows motorcycle headlight modulation systems all 50 states provided they comply with the standards set forth in this section. Title 49 USC 30103 (b1) (US Codes) prohibits any state from forbidding a system that conforms to FMVSS 108.
Code of Federal Regulation - Title 49, Volume 5, Parts 400 to 999 - Revised as of October 1, 2000
From the U.S. Government Printing Office via GPO Access [CITE: 49CFR571.108] [Page 236-307]
TITLE 49: TRANSPORTATION - CHAPTER V, NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
PART 571, FEDERAL MOTOR VEHICLE SAFETY STANDARDS - Subpart B--Federal Motor Vehicle Safety Standards - Sec. 571.108 Standard No. 108;
Lamps, reflective devices, and associated equipment - S7.9.4 Motorcycle headlamp modulation system.
S7.9.4.1 A headlamp on a motorcycle may be wired to modulate either the upper beam or the lower beam from its maximum intensity to a lesser intensity, provided that:
- The rate of modulation shall be 240 ± 40 cycles per minute.
- The headlamp shall be operated at maximum power for 50 to 70 percent of each cycle.
- The lowest intensity at any test point shall be not less than 17 percent of the maximum intensity measured at the same point.
- The modulator switch shall be wired in the power lead of the beam filament being modulated and not in the ground side of the circuit.
- Means shall be provided so that both the lower beam and upper beam remain operable in the event of a modulator failure.
- The system shall include a sensor mounted with the axis of its sensing element perpendicular to a horizontal plane. Headlamp modulation shall cease whenever the level of light emitted by a tungsten filament light operating at 3000 deg. Kelvin is either less than 270 lux (25 foot-candles) of direct light for upward pointing sensors or less than 60 lux (5.6 foot-candles) of reflected light for downward pointing sensors. The light is measured by a silicon cell type light meter that is located at the sensor and pointing in the same direction as the sensor. A Kodak Gray Card (Kodak R-27) is placed at ground level to simulate the road surface in testing downward pointing sensors.
- When tested in accordance with the test profile shown in Figure 9, the voltage drop across the modulator when the lamp is on at all test conditions for 12 volt systems and 6 volt systems shall not be greater than .45 volt. The modulator shall meet all the provisions of the standard after completion of the test profile shown in Figure 9.
- Means shall be provided so that both the lower and upper beam function at design voltage when the headlamp control switch is in either the lower or upper beam position when the modulator is off.
(b) Instructions, with a diagram, shall be provided for mounting the light sensor including location on the motorcycle, distance above the road surface, and orientation with respect to the light.
Headlight Modulator regulations (Canada)
Transport Canada Technical Standards Document No. 108, Revision 4 - Lamps, Reflective Devices, and Associated Equipment
S7.9.4 Motorcycle headlamp modulation system
S7.9.4.1 A headlamp on a motorcycle may be wired to modulate either the upper beam or the lower beam from its maximum intensity to a lesser intensity, provided that:
- The rate of modulation shall be 240 ± 40 cycles per minute.
- The headlamp shall be operated at maximum power for 50 to 70 percent of each cycle.
- The lowest intensity at any test point shall be not less than 17 percent of the maximum intensity measured at the same point.
- The modulator switch shall be wired in the power lead of the beam filament being modulated and not in the ground side of the circuit.
- Means shall be provided so that both the lower beam and upper beam remain operable in the event of a modulator failure.
- The system shall include a sensor mounted with the axis of its sensing element perpendicular to a horizontal plane. Headlamp modulation shall cease whenever the level of light emitted by a tungsten filament light operating at 3000 degrees Kelvin is either less than 270 lux (25 foot-candles) of direct light for upward pointing sensors or less than 60 lux (5.6 foot-candles) of reflected light for downward pointing sensors. The light is measured by a silicon cell type light meter that is located at the sensor and pointing in the same direction as the sensor. A Kodak Gray Card (Kodak R-27) is placed at ground level to simulate the road surface in testing downward pointing sensors.
- When tested in accordance with the test profile shown in Figure 9, the voltage drop across the modulator when the lamp is on at all test conditions for 12 volt systems and 6 volt systems shall not be greater than 0.45 volt. The modulator shall meet all the provisions of this TSD after completion of the test profile shown in Figure 9.
- Means shall be provided so that both the lower and upper beam function at design voltage when the headlamp control switch is in either the lower or upper beam position when the modulator is off.
, so I now have the modulator to make me a little more obvious 
