RH Headlight not working, suspect dodgy ground.

Sargo · May 18, 2023

Hi,

Replaced my H3 bulbs after one blew with some H3 LED's.
The LH side (looking at the front of the bike) works fine but the RH side does not work. These is 12v to the bulb but it seems the ground is less than ideal. Has anyone come across this problem and solved it? If so can you direct me to where the likely earth/ground serving this circuit would be so I can give it some Love?

Bike is an 02 XB9R.

Any help appreciated.

Sargo.

chief_of_smoke · May 18, 2023

I just did this kind of fix on my '04 12r. There is a plug under the fairing. This plug has only 3 wires. The ground is factory spliced and split in the harness between the headlights and the bike. So both headlight share the same ground. There are a couple of options to fix it.
1. But a new headlight harness. (Ebay, St. Paul Harley)
2. Build a new headlight harness. The plug and pins can be found on Digikey. I can't remember the part number off the top of my head. This is the route I took.
3. Almost the same as 2, but fix the factory splice.
4. Find a new ground point, and re ground the headlights.

Cooter · May 18, 2023

Since the ground wire to the second headlight is maybe 4" long(?) from the splice, it would be easy to see if it's compromised, or test it for continuity , or jump it with a 4" long wire from ground to the headlight pin to check it.

I'm betting the low-beam is on.:black_eyed:

Sargo · May 18, 2023

Thank you Cooter, thank you Chief of Smoke, will head back to the shed and test both these remedies. Much appreciated

chief_of_smoke · May 18, 2023

No worries

Sargo · May 18, 2023

Just an update, only getting about 10v to one side and 12,5 volts to other???
(12 volt side is the one that is working on high beam, 10 volt side should be always on (low beam). ???????

34nineteen · May 18, 2023

Sargo said:
Just an update, only getting about 10v to one side and 12,5 volts to other???
(12 volt side is the one that is working on high beam, 10 volt side should be always on (low beam). ???????

There should not be a "10 volt side"

Who do I talk to so we can get a facepalm emoji?

Sargo · May 18, 2023

Oh dear, well aware that 10v to one side is not normal. Thank you for your input.

Cooter · May 19, 2023

It's coming 'through' the other bulb with the ground wire

Sargo · May 20, 2023

Update, still scratching my bounce, no voltage at all on low beam, only to one side on high beam which is correct. Switch seems to have 12v on low beam (yellow wire). Seems to evaporate somewhere between the switch and spade socket connection to the H3 bulbs. Doing my head in…

chief_of_smoke · May 20, 2023

It's is definitely the ground. That is the same issue I was having before I made my own headlight harness. But mine was on the high beam side. To rule out the main harness, unplug the headlight harness. Use small needles or t pins and check voltage at the connector. My failure point was the headlight harness grounds.

Sargo · May 21, 2023

Hi all, thank you for you input. Turns out I had a wire that quit in the headlight harness. Bypassed and isolated it and now all good.
Cheers.

RH Headlight not working, suspect dodgy ground.

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