Modern Vespa

Hi, newbie to the scooter world, just got my son a 2012 fly 2 stroke to get to college, it was cheap so can't complain,
Was told it had a charging fault, shouldn't be too difficult to fix.
Headlight and rear light very dull, charges ok at 13.8v with some revs on, starter works fine etc
However new regulator, new stator, and its still the same, stator is putting out 34v ac down the yellow wire to the regulator but yellow/black is 3.8v ac, exactly the same as the one I swapped it for,

Really struggling now and need some help

Thanks in advance

Suggest confirming a solid ground wire to the headlight - perhaps to the point of running a secondary, temporary ground to the headlight from a nearby bolt in the metal frame.

Could be as simple as a bad connection (think: wire that is pulling out of a crimped eye) between the regulator and the bulbs.

Hi Thank you for the reply,
I have tried a earth straight to the negative on the battery,
The other strange thing is all 3 wires to the headlight and everything else on the yellow/black wire is showing as a negative with the powerprobe,
If I put 12v down the yellow/ black the lights come on at full power, but then the battery voltage drops to 8.5v and then trips the fuse. Just as it did before I fit the new stator.
Very confusing

Are you certain that the regulator's connections are all in place? And that there are no shorts in the form of chafed insulation, etc?

Unexpectedly low voltage and blown fuses are symptoms of a short circuit.

The headlights are AC powered - perhaps you thought they were DC powered?
And yes, they are dim on an ET4.

I have checked as much of thee wiring as I can so far, going to remove foot plate tomorrow,
Fuse that pops is the inbuilt power trip in the powerprobe.

Could it be a broken wire? Continuity check
would it melt a wire if it shorted out to the frame

I was going to replace the bulbs with leds, tried the sidelight first as I had a led bulb and there isn't enough power to turn it on,
Put it in my bike or wire to battery and its on so not faulty,

I know it won't be great but it's really dull, might as well put a candle in there, thats not really a exaggeration

Thank you
Do you know what the voltage should be out of the regulator to the bulbs its 3.8v ac

The LED bulbs probably require DC.

say what? AC powered headlights? I don't believe that

It is true, and not that rare. My RE Bullet, Bultaco and Benelli also had AC lights.

Headlights on small engines are often AC powered, directly off the stator. This prevents the relatively large current draw of the headlight from depleting the voltage from the relatively small battery when applying the very high current draw from the starter motor.

OK so problem sorted,
Took the whole thing apart, traced all the wires and checked continuity throughout.
No faults found,

So started disconnecting plugs and checking the output, probably should have done this earlier,
Disconnected the headlight bulb and bingo, rear light comes on bright with sidelight, increase in output from rectifier,

When we bought the scooter we got a box with some bulbs and old brake pads that had been changed recently but still lots of pad left, a disk lock the guy used etc

Changed the headlight bulb from 1 that looked like a old tungsten bulb to the one in the box of bits, main beam has blown, but it looks like a halogen bulb, and bingo bright headlight, sidelight and rear light,
So previous owner had swapped the bulb and got the wrong one,
Really annoying as I have replaced the stator, relay and rectifier for nothing,
Ahh well at least it's sorted.

Thank you for your thoughts and ideas

well I'll be damed I just looked thru the technical manual for the ET4 and sure enough the headlight AND heater choke circuit are both A/C.

And that, my friend, is why we all value Modern Vespa. Something new to learn almost every day.