Dim headlights and no voltage on yellow stator wire

[moisesanguiano]

Hey all, new member and first post. I want to start off by thanking everyone, this forum has helped me a lot fixing up my scoot. So I picked up what I believe is a SunL scooter, model sl150-21b. I've had it for about 2 months now and it has been running good, after initially dropping in a new carb, stator, and other small fixes. Since getting it running, I've had the dim headlight issue just as so many others have. At idle it's very dim, and of course when I rev they get nice and bright. They don't get bright/dim when I hit the brakes or flashers or anything like that, so that's less to worry about. I decided to take her apart and revisit the stator. Im running an 8 pole, 5 wire stator (3 wire plug with 2 separate wires). Everything seems fine, until I did a voltage check on the stator wires. I'm only getting ~11 volts ac from the white wire, no voltage from the yellow, no more than .5v ac on the blue/white pickup wire, and over 100v ac from the red/black power wire (roughly around 130-140 volts). I've seen a graph that shows the proper stator voltages, and it should be 50-100v on the power, 20v from the white, 15v from the yellow and up to 1.5v on the pickup trigger. I even put in a different stator and got the same result. It seems weird that there's no voltage on the yellow wire yet the ac powered lights still function. I also checked voltage at the regulator (4 pin). No voltage from the yellow, 11 volts ac from the white, and ~13v DC from the red wire. I just want my lights to not be so dim. Anyone knows what's going on and what I need to do to fix it? I have discovered looking around on the Web that there's apparently 2 kinds of 8 pole stators, floating ground and center tap. Still not 100% sure what the differences in use are, but it seems my stator is the floating ground type, as there is no coil wire connected with the ground, and there's only one coil wire with the yellow, unlike the center tap that has two.

[DisillusionedPrepper]

Hi Moses,
I read your post twice so I think I know what you have there.
First off your lighting is running on DC voltage after the rectifier/regulator. They are running off the battery when you disconnect the stator.
Some of these China scoots are wired that way.

I think there are something like six different stators, and as many more ways of wiring these things.

Are you reading your voltages at the stator wires directly (unpluged) or are you reading thru the connector(s).
The reason I ask is I have had several scooters that had faulty crimps on the connectors where they looked like good connections but they were actually just crimped on the insulation.
That is the ONLY reason you would have nothing on the yellow wire unless you have two bad stators.

There are just as many goofy color codes as there are scooter brands so I would NOT trust the graph you found.
It sounds like you have a 1/2 wave floating ground stator. Otherwise it would have a green (ground) wire in the plug, so your voltages sound right for idle. The yellow is your 1/2 wave out.

As far as the blue/white trigger wire... If the scoot is running it is fine no matter what the graph says. That is your trigger for the cdi. It controls the spark timing.

The only cure I have found for low lighting at idle is to convert the entire bike to LED lighting.
It is as cheap as dirt to convert, and the only odd part required is an electronic flasher relay from Ebay. You'll see them listed for about 4 bucks/free shipping.

Here's a youtube link that will get you started on more stator info.

This is NOT the best link but follow the related links, and you will quickly become expert on these crappy stators.
There are several vids on converting to full wave, and changing from common to floating ground, ect.

Just post up if you have any more questions, I'm happy to help if I can.

[moisesanguiano]

Hello DisillusionedPrepper thanks for your reply. I checked the voltage both plugged and unplugged and still nothing. I even did a continuity test to make sure there were no breaks in the wire. Oh and there is a green ground wire in the stator plug, my mistake. About the DC lighting, my brake light and blinkers run with the ignition on engine off, but the tail, dash, and headlights are ac since they don't work with the stator unplugged while the engine is running. I do have an update though. Oddly enough, I switched the yellow and white stator wires at the regulator, and as soon as I turned on the engine the lights were bright! I gave it some throttle and they got a bit brighter, but no blowouts. I checked voltage at the battery and confirmed it was charging. I still need to double check voltages throughout the scooter to make sure everything is working fine as it is, but I'm not sure if there will be long term effects if I keep the wiring like this. Oh another thing I may need to note. So my scooter has one big round headlight, and a much smaller light right below it(I've added a pic from the web). There's 4 wires in the plug, yellow and white (stator ac), blue (from high-low switch I believe), and a green ground which branches off to two wires. The white, blue, and green go to the main headlight, and the yellow (which actually changes to brown after the plug) with one of the greens go to the small bulb. I've always heard that the yellow stator wire powered the headlights on these scooters, but on mine the white powers the main light while the yellow powers the small light (i believe it's like w5w 5 watt bulb). Does this wiring configuration sound right or is there something wrong?

[DisillusionedPrepper]

Here's a better link that I think applies to what you have.



With so many combinations of parts, especially with vendors on Ebay not being sure what they are selling, you could have any combination of stator/rectifier.

I know people like to know exactly what is failing, and why but in cases like these I always simply buy all new parts, and throw the old ones into a WTF bin.
The parts are cheap enough to buy a stator/rectifier, and swap out what you have.

[moisesanguiano]

Very informative video, thanks. I dont have the same stator as his though, so the conversion wouldnt apply to my scoot AFAIK. I switched some wires around to see if it would help at all, but the only thing that seems to fix the issue is swapping the yellow and white stator wires at the regulator like before. I took the scoot for a ride the other day, and it ran good, and the headlights seem to be working great. I do agree about swapping for new parts, so if the current setup ends up failing, ill take your advice and get new parts in there. Thanks for your help!

[Bigpig41]

Realize this is an ole thread, but on the subject of trying to differentiate the yellow and white power wires coming from the stator.....I have a question . I have a 2013 Bashan 150cc scoot that I lost all electrical activity on except the headlights. Unplugged the New stator plug at the wiring harness and the voltage reg. from its plug on the harness. While testing the now separate yellow and white wires in the harness I think it's the yellow that is continuous with ground or only has one or two OHMS of resistance to ground. Is there any reason it should go to ground with both ends unhooked? Is it the fact that per the video in this thread the yellow wire out of the stator is connected to the headlights through the "tap" . Does the yellow wire find ground through the two high resistance filaments of the headlight bulbs when the voltage reg. and stator are unhooked? I've also unhooked the electric choke in case it's providing this ground source I'm trying to track. Thanks in advance for any help as i'm looking for any excuse to not have to dissect that entire wiring harness between the upper passenger side frame and the upper steering column. Also of note it may be important that I've run for a long time with NO battery ! Does that mean any electrical power was having to come out of the voltage reg. RED wire to power this stuff?