Headlight and tail light not working

Eucl1d · Apr 12, 2019

Hi all,

I'm hoping someone has run into this issue before and is able to point me in the right direction of, what I hope, is an easy fix.

My headlight and tail light/brake light on my 2007 FS550 have stopped working. I thought this was due to a dying stator as I measured the resistance on it and it was out of the expected range on a couple of the circuits.

I've just replaced the stator with a brand new OEM unit but the problem has persisted.

In all other respects the bike runs perfectly. Also, if I flick the headlights on to high beam I see that the blue high beam indicator illuminates (although it does seem a little faint). Not sure if this is relevant but thought I'd mention it just in case it's relevant.

Any ideas on how to fix this?

I understand that the headlight and tail / brake light circuits are AC and fed directly from the stator.

Eucl1d · Apr 12, 2019

I've studied the wiring diagram closely and I think it's the left switch block causing the problem. I'm going to start with that but might just be easier to order a replacement and be done with it.

Taffy · Apr 13, 2019

your left switch has nothing to do with your brake lights.

your problem is either a coincidence of two things or the live feed has stopped.

live feed = the red/yellow. you haven't mucked about with a spare red/yellow Jack behind the radiator or a yellow/black which should neither be doing anything? (unless you fitted a fan inline)

Taffy

Eucl1d · Apr 13, 2019

Thanks Taffy.

I did some more testing and I am absolutely stumped here. I've tested all the switches and they all work fine. They're showing continuity/none when they're supposed to. I also have ~20V coming out the yellow wire from the stator and then there's also 12v at 3-wire socket for the headlight and at the tail light socket so I really am at a loss here. It makes no sense to me.

I thought maybe it's a coincidence that both the front LED headlight and the rear LED tail light failed simultaneously but this can't be the case because, for some unknown reason, when I fired the bike up after checking things the headlight flickered on for a few seconds before going dark.

If no one has any ideas then I think I'm going to have to find an auto electrician.

Rainerio · Apr 15, 2019

Look to see if you have any bare wires grounding/earth. Had front blinkers not working turned out to be pinched wires by fork stop.

Taffy · Apr 15, 2019

interestingly, all I am interested in is the yellow/red wire and what is the only thing he doesn't mention.....

Taffy

tinwelp · Apr 15, 2019

Curious. If you have 12V at the headlamp socket and similar at the tail light socket... but you have no lights... have you tried the obvious solution of replacing the bulbs?

If I understand correctly you were using LED bulbs. Be aware that some LED lamps are particularly susceptible to over-voltage, and some types really don't like being driven by AC. So if your lights are directly driven by the alternator (as some versions of the bike are), or your regulator is not doing its job well, that could be the source of your issues.

Try some boring filament bulbs and see what happens. It may help diagnose the problem.

Cheers... Paul

Eucl1d · Apr 26, 2019

Righto, turns out that both the front and rear LED lights were poked for different reasons, but both failed at the same time.

I was running a Cyclops unit on the front, the problem on this end is there's a short in the 3-pin Cyclops plug that connects to the bike's loom. I removed the lot and plugged a standard HS1 bulb into the loom and it's now all sorted.

As for the rear, which is DRC unit, there's no continuity, so something's stuffed inside it. I've ordered a whole new integrated Polisport tail light to replace it.

Thanks everyone for the help and pointers. A good lesson in the dangers of making assumptions!

The standard HS1 bulb is only 35w/35w, is there any risk/issue with swapping it for an H4 which is 60w/55w?

Taffy · Apr 27, 2019

I would think you can melt the clear perspeex or make it turn white.

do you really need such a strong bulb in there? maybe look for something in between but I have plenty of SM bikes here that have a blind (white) spot in front of the bulb now.

cheers

Taffy

FE350 · May 5, 2019

Saw something in the post about an AC circuit and LED. A tad bit of an issue here

LED's are diodes and diodes pass electricity in one direction only. AC current generated by a bike reverses direction with a variable frequency related to engine speed. The LED's would be "on" while the current is forward biased, and off when it reverses, so in reality they will be blinking on/off at at rate so high that it will appear that they are "on". However, they won't be as bright as with DC, (I am thinking the LED's will fail after short use??) from being switched on/off a zillion times? Anyone? Sorry if this has been answered as didnt read full post ? All in all, leds do not work with AC and will always fail in time.

tinwelp · May 6, 2019

Some LED packages include an on-board driver, and these can easily be configured for AC, but generally if you are talking just about the LED, then yes you are almost correct. Providing the peak current doesn't exceed the specification of the LED, there's no reason why driving then with AC will cause early failure.

A lot of the headlamp type LEDs have quite sophisticated drivers, and at least a few can be used with the type of 'direct lighting' employed on the Huasbergs of this era. Google wisely, ask the right questions, and choose appropriately for the best results.

Cheers.. Paul

Headlight and tail light not working

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