Headlamp dims sometimes while riding

I have noticed something odd yesterday. While riding on the freeway I noticed my the road in front of my bike get darker, and then a second later bright again. At first I thought someone was flashing me from behind. But checking my side mirrors, no one was behind me. So the next time it happened (dimming and bright again) I figured it had to be my bike's headlamps.

As per bikerdude's recommendation I wiggled the wire from both bulbs to see if I could replicate the dimming. Everything was fine, no dimming occurred while parked. Could be a regulator, a fuse, or battery perhaps?

My bike is fairly new just over 3000 miles on it and still under warranty.

what rpm is normal for you? is this just after extended freeway riding? if it happens again try to downshift (bring up revs) and see if it continues....

madmanmaigret said:

what rpm is normal for you? is this just after extended freeway riding? if it happens again try to downshift (bring up revs) and see if it continues....

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Interesting point my rpm range is usually in the 6, 7, and 8 K rpms. If the rpms are higher will that provide more electricity?

that usually happens when your radiator fan starts running to cool down..it draws more electricity causing your lights to dim,,and as soon as the fan stops your lights become normal....i never experienced it on my FZ6 yet but almost on every bike i owned, it happened...it also causes your idle to drop a little bit too if you are waiting on a light or something....of course i dont see any reason for the fan to start if you are going on highway speeds and this dimming happens..

Actually it is only the H4 bulb side that the lowbeam does not turn on. I did the Dual Headlamp mod. Some connector is loose perhaps. The high beam works fine on that same H4 Bulb. I guess I will have to lift the gas tank up again...

Where is ground on the bike?

As my right headlamp (H4 bulb) does not turn on; not even high beam works, I will check the wire with a voltmeter. Does anyone know where the ground is on the bike?

nimzotech said:

Interesting point my rpm range is usually in the 6, 7, and 8 K rpms. If the rpms are higher will that provide more electricity?

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no but if they were lower it would provide less.


from your other posts it sounds like a connector is loose or something.

Here's the easiest place to make the measurements while the bike is running.....

When the switch is set to low beam, you should see 12V across the "battery ground" (black) to the "low beam +12V" (green).

When the switch is set to high beam, volt should be 0V across above mentioned while seeing 12V across "high beam +12V" (black/yellow) to the "battery ground" (black).

Re: Where is ground on the bike?

nimzotech said:

As my right headlamp (H4 bulb) does not turn on; not even high beam works, I will check the wire with a voltmeter. Does anyone know where the ground is on the bike?

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usually you can use the key in the ignition as ground for testing.

biker_dude43 said:

Here's the easiest place to make the measurements while the bike is running.....

When the switch is set to low beam, you should see 12V across the "battery ground" (black) to the "low beam +12V" (green).

When the switch is set to high beam, volt should be 0V across above mentioned while seeing 12V across "high beam +12V" (black/yellow) to the "battery ground" (black).

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now if the high & low beam are on at once wouldn't it give you a 12v reading on both with the switch on high beam? or am I mis-interpeting something?

madmanmaigret said:

now if the high & low beam are on at once wouldn't it give you a 12v reading on both with the switch on high beam? or am I mis-interpeting something?

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In nimzotech's case, his RHS hi/lo is controlled by the handlebar switch. The switch will only allow voltage to the one selected, not both.

Consider another possibility, which is that you have a loose connection in the charging system. This would cause you to lose the alternator's output for a moment, and the bike's voltage would drop from 14 down to 10-12, dimming the headlights in the process.

Fred

Just an update. I had a LoJack inspector do a quality check on my dealer-installed lojack unit today. He happened to have a volt meter at hand. So I ran the volt meter check at the H4 bulb wires. With the bike ON we had voltage going across the dual headlamp harness bikerdude sent (lowbeam) and factory wires (highbeam). This proves that my handy work and BikerDudes excellent harness are not loose or at fault.

Is it safe to say the bulb burned out? Seems logical but awfuly soon, given that I bought the bike late January this year. Hmm...

Thank you bikerdude! I know you mentioned bulbs wearing out early on. I am awaiting my HID kit and a Sylvania Silverstar that will replace the assumed faulty H4 bulb.

nimzotech, if it makes you feel any better, my brake/taillight went out with less than 1000 mi on my bike. prob less than 1 1/2 months.

nimzotech said:

Just an update. I had a LoJack inspector do a quality check on my dealer-installed lojack unit today. He happened to have a volt meter at hand. So I ran the volt meter check at the H4 bulb wires. With the bike ON we had voltage going across the dual headlamp harness bikerdude sent (lowbeam) and factory wires (highbeam). This proves that my handy work and BikerDudes excellent harness are not loose or at fault.

Is it safe to say the bulb burned out? Seems logical but awfuly soon, given that I bought the bike late January this year. Hmm...

Thank you bikerdude! I know you mentioned bulbs wearing out early on. I am awaiting my HID kit and a Sylvania Silverstar that will replace the assumed faulty H4 bulb.

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the bulb could have burnt out if anyone at any point touched the bulb. the oils on skin will cause the bulb to burn out very quickly. As a precaution i wipe all of my bulbs with alcohol wipes before installing them.

You can sometimes tell too if the bulb is burnt out by removing it from the housing and look at the filaments. You can normally spot a break in the coily things. Seeing as both have burnt out (odd) then I agree with reiobard in that oil got onto the bulb and she fried. Touching halogen bulbs with fingers is a no no.....

i think your easiest way to solve a problem like this is to start with the whole electrical system and eliminate things as you go.

is it only the headlight that dims, or all the lights? a problem with everything points towards things like the battery, regulator or charging coil.
if its only the headlights, that isolates the problem to that circuit only. id be looking at grounds, fuses and switches. a wiring diagram and a digital meter that measures voltage and resistance will be very helpful.

you said you had a meter connected to the headlight and there was voltage present, but since your light is only dimming, the will always be voltage to the bulb, even when the problem is occurring. the key is what is the voltage.
with the bike running you should be reading around 14-15 volts, anything less is a problem. with the bike off, a fully charged battery is 12.6v, this could be a little higher if the bike was just running, or a little lower due to the load on the battery, but you should still have at least 12.0v.

id be looking at corroded connections or switches and especially the grounds and battery connections. the fan was mentioned earlier, which is theoretically possible, but i doubt your fan is coming on while cruising at highway speeds, and shouldn't have a noticeable effect on a properly functioning charging system.
have you modified or added anything else on the bike electrically?

Thanks for that in depth electrical and logical advice. When the Volt Meter was used the Voltage reading was around 13 Volts, when the bike was ON. I have a favor to ask you when you get a spare chance. Go over to your bike and turn it on, and start the engine. Now turn on your left or right blinker. At the moment the blinker actually blinks, I notice a very minimal decrease in light output via the headlamp. It is very minuscule, but now noticeable to my eye. Do you notice that on your bikes?

unfortunately im in Honduras right now and about 10000k away from my bike.
sorry.
the charging system doesnt put out much at idle compounded with the added load of 2 headlights going so im not surprised that your turn signal/stoplight/fan would have an effect. 13 volts is low for normal rpms, but again it was at idle (i assume) so thats ok. i dont have a manual in front of me, but you should be seeing between 14-15v while at normal operating speeds.

my GUESS is that its one of two things; the voltage regulator, or a poor ground/connection somewhere.

id start by going over all the connections and make sure they are clean and tight. battery cables, fuses, connectors, switches. especially where youve modified the harness. using some dielectric grease on all connections is a good idea. it keeps water out and prevents corrosion.

biker_dude43 said:

You can sometimes tell too if the bulb is burnt out by removing it from the housing and look at the filaments. You can normally spot a break in the coily things. Seeing as both have burnt out (odd) then I agree with reiobard in that oil got onto the bulb and she fried. Touching halogen bulbs with fingers is a no no.....

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You're right!


My HID kit and the Sylvania replacement should be arriving early next week. This was good timing for this bulb to burn out. :thumbup:

Thanks everyone for excellent advice and suggestions.