Headlights & Stator & Rectifier
 

I bought a 2008 Shenke 150cc scooter and what I noticed right off the bat is that the headlights were super dim at idle and not very bright when revved up. I rode it home (about 25 miles) and I also noticed that when I grabbed the brake the headlights became bright. I thought it was a problem with the ground so I traced & cleaned with a wire brush the negative lead from the battery, the wire to the frame, and the wire to the engine.

This did not resolve the issue. I know the headlights work off the A/C circuit and the tail and turn lights work off the D/C circuit. Now at an idle the headlights are off. When I take off from a stop sign the headlights come on but are very dim. When I hit the brake lights (While cruising at about 6k RPM's) the headlights become bright and stay that way until I come up to a stop sign again and then they dim and go off again. It seems that the only way I can get the headlights to come bright again is to hit the brakes when I am above 4k RPM's or so.

So where is the most likely spot to start diagnosing? I already ordered a new rectifier cuz they are cheap. Is it possible/likely that I have an issue with my stator? How do I even test my stator?

-Crash

I would guess on the VR.
And the only real way to test the Stator, is to replace it. :(

Also, I had a problem with my lights blowing when I revved the bike.
Turned out that my tail light had a short in the contact. That caused my head lights top blow as well.

Still Don't Know
 

So I have changed out the rectifier, removed the stator and cleaned it up, inspected it for broken or worn wires, and put it all back together. Still having the same issue. Last night while driving home my headlight, marker lights, tail lights, and dash lights were all dim. I grabbed the brake and it was like a light switch came on and everything was bright as I cruised across the bridge at 55 mph. When I came to the exit ramp and around a sharp corner letting my rpm's drop below 2k, the light switch went off again and everything was dim. Then as I cruised down the street I pushed my emergency flasher button and everything was bright again.

I don't know what else it can be. Anyone have any more ideas? Maybe another bad rectifier? A bad stator? Wired wrong? Maybe this scoot is just cursed.

-Crash

I have the same problem when I use my turn signals. Started noticing it after I replaced the lighted mirrors with non lighted ones. However the headlights don't dim at all if I have the stereo amp on drawing 2 more amps. Could it be that a minimal draw is required to make the regulator work right?

I don't believe there is a 'minimal' draw requirement..
But with the statement of the stereo, I have to guess myself now.

Unless, you have a bad ground somewhere, and turning on the stereo might activate a new ground?.. Im kind of a little dumbfounded here.
If you have cleaned every grounding point, and filed of the paint, but it still does it, when its running, wiggle the light bulbs, pull them out, or twist them.
just be careful, as they get hot..
(^ Just so we can be 'Politically Safe.. lol)

Could be because I run 35w bulbs instead of the 25w stock bulbs. However I never had a problem till I took the lighted mirrors off. The wife still has the lighted mirrors on her's with the 35w headlamps and no problems. But thats for another thread.

No, those bulbs wouldn't matter.
Could you buy new mirrors?

Well now I am going to add a little more to the mix. I intentionally drained my battery down to 11.5 volts by leaving the emergency flashers on yesterday while at work. They blinked for about 3-4 hours. Battery was at a solid 12.9 volts prior. When I took off from work the headlights were bright. As I pulled up to a stop sign the normal dimming would occur and then when I took off again they were all bright.

So why would the A/C headlights, tail light, and dash lights be affected by the amount of DC amps drawn through the system? Yesterday was the first time in a while I was able to maintain bright headlights and dash lights all the way home without fail. I am assuming the same about my tail light, but I'm not quite dumb enough to turn around and look at it while cruising down the road at 45mph.

Sounds like a bad connection to your headlights that is resolving itself when you activate another circuit. Look for a pinched wire or bad connection. Wire terminals are often at fault but look ok at a glance. Thin gauge stranded wire can break inside the insulation leaving only a strand or two to carry all the current. Take the plastic off the headlight and move the wire harnesses around with the engine running and see if the headlights get brighter. Use a good piece of wire between a wires terminals to test a wires integrity. Logic can not be your only tool with these oddball circuits because when you do find the problem you will most likely say "go figure".

Well, I am baffled now.
DW has the last thing I would accept for a fault.
Sorry, I don't think I can be of any service. :l

I am going to tear into it tomorrow morning. I have a 2nd new vr on order that will arrive tomorrow as well. I know that the stator is doing a good job keeping my battery charged. The resting voltage is 12.9v. With the battery partially drained the headlights and dash lights act as I would expect them to, to dim at idle and to get bright when I take off and cruise, but this only happens when the battery is drawing amps to become fully charged. If I trickle charge the battery over night to 100% then the headlights and dash lights go back to extremely dim at cruising and off at idle.

Tracing wires and then replace the vr again tomorrow. Will post the results.

Thanks guys!

So I installed the 2nd new voltage regulator and now the headlights and dash lights stay on when I pull up to a stop sign, but they are about 50% of their potential brightness. They do not get any brighter when I rev up the engine. Still stumped. I am going to pull a voltage test coming out of the stator and see what is going on there. If the stator is producing the desired voltage prior to it running through the regulator then the only thing I can assume is that the regulator is screwed up.

Taking it to a repair shop on Saturday. I am out of options.

https://lh5.googleusercontent.com/-p...6Schematic.gif

As you can see, one wire from the stator (yellow) powers many of the lights (including headlights). From your description, you are getting an intermittent draw, dimming your headlights.

Since the headlights don't go out completely it is safe to assume that the yellow wire is intact and not grounding out. However, if the voltage regulator were leaking too much power to ground, it would cause the same issue. You stated that you replaced the regulator. In this A/C circuit the rectifier serves to dump excess power to ground, giving you 13VAC to your lights. If this fails, all the power goes to ground and can burn your coil windings in the stator.

There is also a ground screw on the stator that is subject to vibration.