Bonneville America Forums Forums Technical Forums General Tech I'm Lost

I lost headlight functionality, I get 13 volts to the bulb plug, engine off, ign on, The bulb works (tests out) with jumpers from a power source and every thing (no exceptions) else on the bike works fine. I can't find a obvious bad plug, blown fuse, bad connection or burnt wire anywhere. Ideas, direction, something to check? I'm listening. Not the ground, it checked good on a ohm meter, but I still ran a jumper, no headlight. Not the relay on the frame spine either, as I had two new spares to try. Also the dimmer switch moves the hot side of the bulb plug as it should. I have a meter, and any suggestions as to where I should probe next, would be much appreciated?

I'm stumped, but I'm thinking long and hard on this one. Everything I want to suggest, you've already done. WTF?

I would take the switch apart and clean the contacts with a very fine emery cloth or even better a craytex stick ( grit impregnated rubber stick). Not much else i can suggest other than making sure all connections/grounds are good.

man thats a tough one. Is there anything on the bulb connections that might be causing a short or bad connection some how that you are not duplicating when by passing it to try it? Anything getting pinched or pulled that might seperate a broken wire or something when you hook it to the bulb? not sure i am being helpfull

Is it possible you have enough coronet ion to tickle the meter to read 13v but not enough to carry 55w current?

Just for grins, did you try another bulb?

Geez, who'd have thought predictive spelling would come up with coronet for current?
I think if you have amperage setting on your meter you have to put the leads in series, I'd choose the ground leg and measure. A chafed wire going thru the grommet in the headlight bucket could easily cause this or a poor ground return from the lamp.

Ohms law says divide wattage by voltage to get current. 5 amps I think would be about right but I'm guessing around 60w for your headlight. If you see 12v at the plug and you're certain both elements in the lamp are good then lack of current carrying ability is the answer. Chafed wire or corroded contacts at the switch become the most likely solutions. A chafed ground would not spark to alert you so I lean towards that as a hard to find problem.

It's got to be poor amperage and if so... why? Where's the current that normally reaches the headlight bulb going to. It has to be a short. There's voltage but no current. I'd be looking for a short.

It will be interesting to see how much amps your meter reads.

Maybe but I was taught a short is voltage going straight to ground. Ryk has a lack of current which tells me not enough cooper between the device and the power source. That might be the ground path too. I suspect he can test between the hot wires to ground thru the meter and see if he can draw the 5 amps and that should tell the story or at least eliminate it so other paths can be tested.

I would make a ground to the motor with the negative probe and start poking around with the hot probe with the meter at some range above 30A since that's our main fuse value. That would eliminate the hot sides, or find the weak spot. It's a mystery now and eliminating suspects is his best path.

Did you find the problem?

No, and it wasn't from a lack of looking. I have a appointment with a bike electrician guru guy Thurs. AM. You were right about the lack of amperage to light up the bulb, it will barely light a diode as is. I will be going to a dedicated circuit, just for the headlight, with a on/off switch on the tank console. Thank you, everyone who volunteered their help.

Darn, I was hoping for a solution to a new problem to add to our collective brain trust. Going with a dedicated relay/switch combination will certainly work and won't be difficult but I want to know why and where the original failure is located. It's a mystery for sure.

Ryk,

I took a look at the print and this is what I see. Since all the other lights work, the only fuse you should look at is the one that powers the headlight - fuse #9. Power comes from fuse #9 and travels to the headlight relay. From there it goes to the "light switch bypass" in the right hand handlebar. From there it travels across to the dimmer switch and splits to either the high or low beam.

First, since the feed to the #9 fuse also feeds fuses 7 and 8 which go to the other lights and they work, this wire is probably good up to fuse #8. Problem might be between fuse 8 and fuse 9. Fuse 9 is the last fuse this wire feeds. Check the back of the fuse box for corrosion.

Second, I would look closely at the wires going in and out of the #9 fuse holder to see if they aren't corroded. Check the fuse tabs for looseness also. I think this is probably where your problem is.

Third, Since you checked the relay by replacing, make sure the connections are good but you already did that.

Fourth, make sure the light switch bypass in the right handlebar control isn't corroded. This is another likely place for corrosion and the problem although I've never looked closely at mine.

Fifth, look at the feed wire going to the dimmer switch in the left handlebar (comes from the light bypass switch). The problem could be on the input side of this switch since both filaments on the bulb don't light up. Another likely problem source.

Whenever you have corrosion in a circuit, it is like adding a resistor to the circuit. If the resistor is in series with the load such as a light bulb, the light may not get enough power/voltage to light up. With the circuit open, you will get 12 volts at the bulb but as soon as you complete the circuit, all hell breaks loose.