At first I thought there was a loose connection and bumps were knocking out my headlight. But I have realized that it always comes back on if I shut down and restart with no appreciable jostling. The headlight will go on and off while riding, usually with several minutes between intervals either way. The low and high beam will either both work or neither will.

Given that the problem is only reproducible while riding, how in the heck can this be diagnosed? The problem disappears at restart.

Is there anything I should try before just taking a gamble on another junction box?

Oh, flashers seem to stop flashing and just stay continuously lit at similar mysterious intervals. I haven't looked at this yet, but years ago some issue was found to merely be the relay vibrating too much and it was solved by securing it to the frame. AFAIK, this would have to be a relay issue?

intermittent faults are the hardest to solve as you never really know when there fixed. I would start by cleaning and adjusting all the connectors so there tight. then replace some of or all the components one at a time. testing the bike in between until the issues goes away. from the basic description it does appear to be some sort of relay fault that gets reset when the bike is restarted. similar to rebooting a computer when it freezes.

sorry this is all I have without more info.

PS, I am struggling here a bit as European models are wired differently to US models. we have a light switch and no running lights. so US models must have some extra relays to control the lights when the engine is started.

I had similar problems with front indicators/running lights, if not the headlight, and it was all due to bad connectors. Specifically, some bullet connectors under the front fairing. I live a humid climate, and I often end up riding in the rain, and I noticed the problem usually occurred in the damp times, though jostling could trigger it. To my eye, the connectors didn't look bad, only very slightly corroded, but they were the problem. .I tried cleaning up the connectors and using grease, but the problem kept returning. In the end I just got better connectors, and that fixed it.

Grab harness wires near headlights and shake them around. Bad connections will cause lights to flicker or go out. Then move down harness 6-inches and try again. There's about 5-ft of harness, so 10 shakes should be able to narrow down problem section.

Can also measure resistance of each wire-segment end-to-end and corroded connectors in between will measure something other than zero ohms. Easy enough to test entire circuits of each light to find out where problem is.

Yes, replacing with better connectors that has seals will fix this permanently.

Standard headlight bulb? LEDs will confuse the reserve lighting device and it will show a 'bulb out' light in the cluster and will switch from low to high beam intermittently. But, it does sound as if a ground of other connection is the problem here. The bullet connectors normally work fine, but are not all that high quality, so connections do go bad over time.


When I re-connect wiring, I routinely pinch the female connectors so that they will make better contact with the bullet.

Wow, I haven't gotten around to this for almost a month! I finally took a looksee today and after seven or so years of ownership realized that there were fuses in that junction box! Well the headlight apparently has had the 30 amp spare in there at least as long as I've had the bike. One other fuse was not fully in, so I just pushed them all in and replaced the errant headlight one. I gave the blinker relay a wiggle and I'll see next night ride if the problem recurs or not. Thanks all!

Yikes! 30-amp is not for headlight! Should be 10-amp. Spare 30-amp is for starter-solenoid.

My efforts were fruitless, so it went to the shop. They tried explaining, and I didn't really follow, but supposedly whatever the gizmo that keeps the light off until the engine is running was deemed the culprit and it was bypassed. And the flasher relay was replaced. Snow promptly arrived, so none of this has been thoroughly tested.