Modern Vespa

Hi All,
So I mentioned the other day that one of the first things that happened while I was out riding my ET was all the lights stopped working.

Well, this is because every light on the bike is blown.

My first reaction was "dammit! Regulator?", but after some reading I think the answer may be more interesting:
I found a broken wire in the headset.
Also, am I correct in understanding that because it's a balanced electrical system, when one bulb blows the others are more likely to go?

I'm looking at the wiring diagram, but I hate those things...



Here's what we find in the headset:

Loose black wire looks like it should go to the pilot bulb. Here's the scooterhelp wiring diagram for a ET3 that shows the ground wire for the pilot bulb. Check all your grounds and make sure they are clean and tight and that will hopefully help with the popped bulbs.

Black should be ground. It's possible, when the ground broke off. All the juice went to the running light and it popped. When the brakes were used that light popped also. Repair the broken ground and use a multi meter or test light to see if have power when your scooter is running.

Almost all of my bikes have regulators. my 1970 had a tail light blow and then all the bulbs didn't work. It has a regulator too, I did not rebuild that bike, it was rebuilt professionally by sportique in CO. Don't be scared of a regulator, it can ease headaches, as soon as we put one on my 1975 I did not have to replace the tail light as often.

The black wire is a ground and is secured to one of the screws that holds the metal plate on top of the throttle and shifter guides.

The blue wire is for the speedo bulb which splits from a red/pink that is connected to the pilot bulb. The blue wire (speedo lamp) is grounded by the speedo itself.

While your at it check the condition of the green kill wire, I had to route a new one 'cause the insulation was cracking.

Here's some posts from nomadwarmachine's thread:

https://modernvespa.com/forum/post1573729#1573729

https://modernvespa.com/forum/post1573737#1573737

https://modernvespa.com/forum/post1762007#1762007

Still can't tell where that ground is supposed to go... Doesn't look like it - on my setup there is definitely one ground terminal on the bulb assembly, with two intact wires running off of it (see pic #1) - there's no extra broken wire or anything on there that I can see. Near as I can tell, with a continuous silver metal between the pilot and main bulb, I think they share the ground Also I don't think so - see pic #2 - that's the ground from the plate holding thing shifter guides in place and it has an intact black wire on it. Maybe this one also ran to that same connector (the one in my fingers), but I don't see frayed wires? Should there be two wires sticking off that terminal?

Lastly, #3 is a shot of the top of the headset - I *think* all the blacks are intact on the ignition switch.

The broken ground wire in question is running straight out of the bundle of wires coming up from the frame seen in pic #3 - you can see it sticking off to the left of the pic from that bundle

Well I pulled my headset apart and couldn't find an extra ground wire like yours. All the lights work the way it is correct? Maybe say fuck it and just tape it off?

Bulb holders the same way

Thanks so much for digging in on my behalf! I wouldn't say the lights work the way they are since the thing that got me going on all this was they all went "pop" while riding the other day. Maybe workED

I actually think I see two blacks in your first picture running off that ground point above the cable guides - am I seeing that right? If so, then I guess that IS where my break came from (it looks so clean - doesn't really look like a second wire's missing there, but I can kind of imagine it if I squint)

Good eye. Yea mine definitely has two black wires coming off of the same screw on the cable guide.

rock on! I'll break out the electrical tools

So, I repaired the black ground - there are now no severed ground wires in the headset. The ohmmeter shows a connection between ground on the bulb assembly and that screw on the plate holding down the cable guides that we've been discussing

I fired up the ET3 and went to record voltage from the rear running light (red arrows pointing to where I put my contacts on the image below). I did this test with no good bulbs in the scoot - they are all blown.

With the right handlebar light switch to the far left position (which is I believe headlight+tailloght), I read ~15 volts there

How is that possible? The scooter is definitely still the original 6V electrical system. Is this because of this whole "it's a 'balanced' system" dealy, and with no good bulbs the voltage isn't dropping across multiple fixtures?

Yes, with no load (burned out bulbs) the AC voltage will be high as you measured.

As often mentioned, a burned out bulb causes others to blow. If a bulb momentarily loses a connection due to vibration or other reasons, the stator sees that as a blown bulb, the voltage rises as you measured, the bad connection remakes and the bulbs blow due to the high voltage. You replace the bulb(s), it works for a while, then happens again. Intermittent connections. Very pesky.

I'm with Nuttmeg. Two-wire AC limiters (regulators) are handy. Since there is more than one stator output from many vintage Vespas, it might take more than one regulator to solve the problem.

A two-wire is simple. If you wire it across a stator coil somewhere on the scoot's wiring that has one side grounded, it works. One wire on the power wire, other on ground. If wired as the top drawing, looks like stator red to ground.

The other output is not grounded (floating). Looks like yellow and blue. You can place a two-wire AC limiter across those two wires without grounding.

Easiest way for me to visualize is that if the bulb doesn't burn for whatever reason, the regulator immediately becomes the bulb (load) until the bulb burns again.


http://www.treatland.tv/yamaha-FS1-6V-regulator-p/yamaha-fs1-6v-regulator.htm

awesome reply blackbart! I'm not sure I understand 100% how to implement the regulator from your description - you're saying it will have 2 terminals (a + and -) and a 3rd dangling wire that doesn't connect to anything? And I need to find a place in the wiring where the regulator intercepts as much of the voltage output as possible?

BB Any way you could draw how you would wire that into a system? I'm confused too. I understand the shunt type regulators with three prongs (in, out, ground) that keep the voltage at a certain limit, but not the one wire zeener diodes or the one that the link took you to.

The 6v AC limiter in the treatland link, apparently a Yamaha unit, has only one wire. The case is the second wire. Mounting the case solidly to metal takes care of the ground connection. The one wire is attached to the power wire coming out of the stator anywhere along its way to the bulb. Seems to be a red wire on the diagram and pictures. Between the red wire and ground. Looks like the red wire can be accessed at the engine j-box or horn. That should protect the headlamp.

http://www.rexs-speedshop.com/XT250-XT500-TT600-Voltage-Regulator-6-Volt

I was WRONG about the yellow and blue floating output, I think. I've never seen an ET3 stator, and the diagram shows no ground on those two coils. Faded memory reminded me of the two coils wound together as one, with one end of each coil grounded. Two varnished ground wires under a screw and two colored wires coming out of the stator from what appears to be one coil. For the brake and tail to work from that diagram it looks like the two-in-one coil deal. Can anyone verify?

If so, that means THREE separate circuits (outputs/wires) with one end grounded. Sorry about that. Three voltage regulators?

Since I have never tried it, someone else can be the experimenter. You could attach the regulator underneath behind the brake/tail, possibly to a fixture stud/screw, and alternate attaching the regulator wire to the yellow or blue wire if one bulb blows. The engine J-box is another possible wire connection point.

I would try yellow first. It has more possible problem points. The blue brake light seems to have a single coil wire dedicated to a single bulb. Easiest to maintain and less sources of trouble. Good connections, good ground.

If a bulb still blows, it MIGHT be possible to connect the regulator wire to both the blue and yellow wires, but I know nothing about phasing between those two coils. Do so at your own risk. The limiter looks like an open switch, or looks to the stator like nothing is attached, until the voltage goes too high. The risk is small, due to the weak stator output. Be brave, and let everyone know if that works or ruins something.