Headlamp voltage when activated

[Mesozoic]

I've almost got my '08 XB12Ss back on the road from a wreck that occurred 2.5 years ago and the last issue is the headlamps not functioning. I measured the voltage output at the headlamp connector and am seeing around 11V with the bike not running, key on. When I plug any kind of headlamp into it, be it an HID ballast, an LED light, or a regular old H7 halogen, the voltage drops to near zero. I think this is some kind of indication that the LiFePO4 battery isn't able to supply the current needed or something, but not sure. I've ordered a new AGM battery, btw... getting rid of the LiFePO4 (hard starting and resetting the dash a lot even though I live in a temperate climate in southern Arizona). Anyone witness anything like this before?

 

[Tbone]

Check the headlight connector, especially the black wire for melting. I just did a re-wiring of the ground wires for the headlight assembly and took them out of the connector altogether. On my 2009 Uly the ground wires were all combined into one 14 to 16 awg into the connector. Best thing I ever done was to ground each bulb of the headlight assembly separately, your bike will thank you.
If you have a melted connector I am going to recommend that this is something to check or modify on every Buell, possibly a headlight grounding Mod. or something?
My Uly Starts with dual headlights better than it ever has with a single headlight as well as improved performance of the lights and the bike.

 

[Mesozoic]

Thanks. I've never dug into the stock wiring for the lamps, but that makes sense... looks like the consolidated the grounds and should've left them discrete for electrical performance reasons. I mean who's going to continue running halogens for the rest of the bike's life anyway. I'll look at my grounds shortly.

 

[Tbone]

I've only ran the basic H7 55 Watt bulbs that are stock, cooked the connector, wished I saved it now to take a pic of the evidence. I love this mod and now that the front end is grounded the H7's work a lot better and no need for hid, led, laser beams, etc... plenty of light out of the stock set up and the bike performs better in all things electrical!

 

[Cooter]

You already bought a battery but the way to check it would be to test the voltage at the battery when you plug in the headlight.

 

[Mesozoic]

I measured a voltage drop of 1.65V between the grounding bolt on the front of the frame and the ground feeding the headlamp itself. That is a ridiculous amount of voltage drop, so clearly that had to be fixed. I created a new 10AWG ground strap that splits into 2 16AWG ground connections, one for each headlamp.

 

[Tbone]

There is a third bulb, at least on the Uly that goes between the headlights, so that is why I made a 3rd separate ground wire for it. Are you doing the Dual headlight Mod as well? I recommend it especially since you are grounding it properly. For that mod you cross the yellow and red wires. For my grounding I removed the black wire out of the plug put it on the bolt head directly to the cross brace behind the wind screen. Then to the same bolt on the nut end put all three bulbs on separate ground wires. All wires terminated with 12 awg ring terminals with 14 awg tinned wire, crimped, then soldered and covered in heat shrink. Removed the ring terminal plastic jackets, they take up too much space.
Before working on my Headlight ground I was reading 10 volts across the headlight ground to battery, 2 volt drop, killed that gremlin and now I read a full 12 volts.

 

[Cooter]

I've tried adding that little vanity light and melted the housing:down:

If you add it, be sure to get a low wattage one. The bulb and socket is easy to find at an auto parts store.

 

[Mesozoic]

I don't know what I had done several years back, but I had some kind of janky diode setup to get the dual headlight mod going. I had to rip all of that crap out, performed the dual headlight mod properly (swapping orange wire with yellow wire in the white Amphenol connector), and use relays for each headlamp as well. Each power feed from the relays to the headlamp has a corresponding dedicated 12 AWG ground. The field coil of the relay doesn't require much current capacity, so I used a consolidated ground strap and eyelet for that using 16 AWG copper. I used a low wattage LED bulb for the parking lamp in the headlight housing. All is working well now, thanks for the input.

 

[Tbone]

Yes I like the bright White Led courtesy light as it gives extra back lighting on Low beam with the DH Mod. Mesozoic you were able to keep the original connector and add relays? Glad it is working well now.

 

[Mesozoic]

Yes I like the bright White Led courtesy light as it gives extra back lighting on Low beam with the DH Mod. Mesozoic you were able to keep the original connector and add relays? Glad it is working well now.

Yes, I was able to retain the original connectors and added weathersealed relays for each lamp's power, plus additional ground straps.