Low beam went out - need some help, please

[Erci]

Low beam just stopped working last night. Of course it was completely dark and I was 25 miles away from home. Just pointed the lights down and rode home with high beams on.

Background: I am running Dual Dominator headlight:

Each side has H4 bulb (both low and high beam). Original Dual Dominator wiring: it only had one three-prong inlet and each of the prongs has 2 wires connected to it. 1 wire goes to left light and 1 wire goes to right light.

I already had BD43's mod done, so I just used my right side 3-prong outlet (3 wires connected and worked on stock setup for both low and high beam). I ran it like this for over a year with no issues.

Now: Low beam does not work on either side. High beam works on both sides.

Here's what I've done so far: pulled both bulbs out and checked them. They're fine. Just in case, plugged another set of bulbs in.. same issue.

Here's where it gets interesting. With both bulbs out, I measured voltage on low beam setting. I'm getting a perfect reading.. 13.6 on both sides. As soon as I plug one bulb in (doesn't matter which side.. I tried both), voltage goes to zero!!

Another thing I noticed which seamed kind of weird to me.. not sure if it's supposed to work like that.. take a look at the picture below:

On low beam setting, 1+2 reads 13.6. 3+2 ALSO reads 13.6, 1+3 reads zero. Could that be normal??

On high beam setting, only 1+3 reads 13.6, all other combinations are zero.

Headlight fuse is fine (obviously). Any idea how I can fix this??

 

[Shamus McFeeley]

This kind of sounds like a ground problem, but I'm not familiar with that style of headlight. Without looking at the diagram, I believe you should have voltage between 1 and 3.

 

[Erci]

This kind of sounds like a ground problem, but I'm not familiar with that style of headlight. Without looking at the diagram, I believe you should have voltage between 1 and 3.

Does the headlight really matter when it comes to diagnosing this? For all intents and purposes, isn't it the same as right (high beam) side of stock FZ6 with BD43 mod?

Is there any way to troubleshoot headlight wiring without starting the bike? I will have to pull the tank up to get to the wiring.. and of course it's full right now.

 

[Shamus McFeeley]

I don't think the bike powers the headlights without being started first. You could start the bike and then use the kill switch. Mine will stay on until I turn the main key switch off.

Honestly, I don't know if the headlight makes a big difference or not because like I said, I'm not familiar with it and I don't know how it is wired.

 

[Ben_H]

It's not a ground problem because the ground is shared for hi and low beam. Just trace wire back to fuse box. Its the only way. When i get back to the shop in am i will look at my manual. To see diagram but should be easy to fix bikes are small and wires are easy to get to compared to cars.

 

[Anthrax]

A voltmetre measures the diffence in voltage between point a and point b. So if you have 13.6 volts at one pin and 13.6 at another your reading will be 0. You need to take your measurements between your pin and a good ground.

 

[Motogiro]

The BD43 wire should be your low beam signal. You should show voltage to ground on low beam. When switching to high beam there should be no voltage between that #2 pin and ground but there should be voltage from your #1 pin to ground.

Make sure you test these voltages with both plugs unplugged from both lamps.
Also PM me your telephone number.

To insure you have a ground run a jumper from #3 pin wire to a non painted metal part on the frame or engine to make sure you have a ground.
Edit: sounds like your low beam( Bd43 wire)may have come out of the harness plug.

 

[skooter65]

Here's where it gets interesting. With both bulbs out, I measured voltage on low beam setting. I'm getting a perfect reading.. 13.6 on both sides. As soon as I plug one bulb in (doesn't matter which side.. I tried both), voltage goes to zero!!

To me, this makes sense If the bulbs were lit. Voltage is measured as a difference in potential energy. Picture the filament in the bulb as a "switch" which completes the power-ground circuit. With the bulb un-installed, the circuit is not completed and the ground will have zero potential while the power side is at 12 volts nominal; or as you had measured, 13.6 volts. With the bulb installed, you are completing the circuit, closing the "swtich" which would be like trying to measure voltage at two points along the same wire which would read "zero".

This tells me that the circuit is "working" in that there is flow of electricity though the circuit. If the bulb is not lighting, that would tell me that the current is too low to illuminate the filament. Since the ground is shared with the high-beam, and the high beam is working, that would tell me that the problem has to be in power-side of the circuit. i would suspect that there is a short either in the low-beam power wire or low beam switch.

I would start by measuring the voltage from pin #2 to a ground on the frame (with the bulb installed). If I am correct, this should measure something less than the necessary 12 volts required to illuminate the low-beam filament.

The next step is to chase the short.

My 20 cents

 

[bd43]

On low beam setting, 1+2 reads 13.6. 3+2 ALSO reads 13.6, 1+3 reads zero. Could that be normal??

On high beam setting, only 1+3 reads 13.6, all other combinations are zero.

You shouldn't be getting 13V between 2+3. I suspect you still had the other light plugged in and you were measuring through the high beam fillament to ground to get that voltage. Try unplugging both and then measure 2+3 again. In any case, if 1+2 is 13V on low beam, your low beam filament is shot. Try measuring the resistance between 1+2 on the bulb. It should be close to a short, otherwise if it's open, you will read infinity....

Try that.

 

[skooter65]

You shouldn't be getting 13V between 2+3....

Unless there is a short on #2.

 

[bd43]

Unless there is a short on #2.

If you mean a short to ground, then 1+2 would not have had voltage. If shorted to 3, then 2+3 would have been 0V. If 3 was shorted to ground, no voltage on 1+3..., either 2 or 3 shorted to ground would surely have blown the fuse.

 

[Erci]

Thank you all!! I'll do some more testing tomorrow (each pin to ground, instead of pin to pin in both low and high) and I'll report my findings!

Cliff, I'll take you up on the phone call if I won't get anywhere on my own.. thanks so much!!

 

[skooter65]

If you mean a short to ground, then 1+2 would not have had voltage. If shorted to 3, then 2+3 would have been 0V. If 3 was shorted to ground, no voltage on 1+3..., either 2 or 3 shorted to ground would surely have blown the fuse.

I am making a few assumptions:

-1: That the switch was in the high beam position when he measured across 2+3.

-2: That the short to ground is not very strong (no a complete bare wire to ground).

 

[Erci]

I am making a few assumptions:

-1: That the switch was in the high beam position when he measured across 2+3.

-2: That the short to ground is not very strong (no a complete bare wire to ground).

1. 2+3 was measured in low beam setting (in original post).
2. Even though setup is custom, I am using ground of the original wiring harness :don'tknow:

I'll be doing more testing very soon. Thanks again, everyone!

 

[Erci]

Latest findings: (please refer to my original post for pin numbers)

Test #1: both bulbs out, low beam, negative needle of voltage meter connected to ground (bolt on frame), positive needle of voltage meter touched to individual pins to test voltage.

Result: pin 1: 0v, pin 2: 13.6v with bike on (12.45 with bike off), pin 3: 0

Test #2: Same setup as first, but high beam on.

Result: pin 1: 0v, pin 2: 0v, pin 3: 13.6v with bike on (12.45 with bike off).

Test #3: Same setup as first (low beam), but one bulb plugged in.

Result: pin 1: 0v, pin 2: 0v, pin 3: 0v.

If I'm not mistaken, first 2 tests show *good* results. What could be making pin 2 go to 0v when bulb is plugged in?

 

[fazed_ya]

It is definitely sounding like a short to ground. Check for continuity while bulbs are in

 

[Erci]

It is definitely sounding like a short to ground. Check for continuity while bulbs are in

I'm hopeless when it comes to electrical work

Here is what I just tried: put one bulb in (I'm not bothering with the 2nd one for testing, since all 3 wires are piggy-backing off the 1st one, I am assuming it's not necessary for the test and I should be able to run 1 bulb.. is that right?)

Completely unplugged ground wire from the inlet. So now there only one hot wire going to the bulb (low beam). Started the bike and held the unplugged end of ground wire up to the frame. Bulb stayed off.

Flipped it to high beam and held the ground wire to the frame. Bulb turned on.

How else/what else can I test? Remember you're talking to a non-electrical person.. I need steps to perform

Thanks!

 

[fazed_ya]

Turn your meter to ohms. Install bulb check across your connections. Meeter should beep with continuity. When it doesn't beep your find your broken circuit .. it sounds like its in the light bulb housing. Also check bulbs for continuity

 

[fazed_ya]

I wish I was there it'd be alot easier ....you have voltage when not installed. Something is shorting across your circuit when in stalled .....


It can't be the switch otherwise no voltage any time ...so its after the switch which leaves the housing or the bulbs.. bulbs you've tested which leaves the bulb housing

 

[fazed_ya]

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