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Discussion Starter #1 (Edited)
I'm just starting apprenticing at a shop and my first real problem here is some electrical in a "1963" (As I've been told) Vespa.

The problem is that there is no voltage going to the brake lights we installed. so Firstly please look at the attached PDF.

View attachment VBB2_VLA1.pdf

I got it from this website, and deduced that the wiring is from the latter link (or see attached PDF).

1960's Electrical Diagrams

Scooter Help - Vespa 150 (VBB2T)

Now. Here's where my problem begins.

The tail light has voltage. And we've tested the black cable to show that current is flowing through that.

Yet what is lacking signal seems to be from the blue wire going to the brake light.

The only thing that's had the brake light work is giving it some juice directly from a battery.

(Yet, the Vespa actually doesn't have a battery)

In my opinion, the problem is that there is no blue wire getting power from the magneto to even send it to the brake light.

This is deduction cam from two factors:

1 - There is only two, not three blue wires at the junction box.

2 - There is NO blue wire by the magnetos.

Whoever fixed this Vespa before didn't do the greatest job. (The kill switch wasn't even wired in)

Anyways, my boss says that we won't be doing any wiring on the magneto. I'm not sure why. Can somebody tell me?

Here are some photos, and I hope you guys can give me some hints as to what's wrong.

I have clipped the brake switch contacts together with alligator clips in case the contacts weren't touching properly when the brakes were applied.

Feel free to also browse this 1962 manual, the two models are virtually the same.

http://www.tamlyn-serpa.com/images/Vespa_150.pdf

image.jpeg image_2.jpeg image_9.jpeg image_4.jpeg
 

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Discussion Starter #2

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The problem is that there is no signal going to the brake lights we installed. so Firstly please look at the attached PDF.
I think you may have it figured out already but some clarification is needed.
By "signal" I assume you mean voltage, which comes from a battery or magneto.

One wire on the brake switch goes to the stop light bulb.
The other wire on the bake light switch must make it's way back to the magneto somehow......maybe through a fuse.
That voltage can actually come from ANY wire that is hot all the time the bike is running.....like the tail light.

Getting it to work should be easy; getting it to work as originally designed might be a tad more difficult.
 

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Discussion Starter #4
I think you may have it figured out already but some clarification is needed.
By "signal" I assume you mean voltage, which comes from a battery or magneto.

Getting it to work should be easy; getting it to work as originally designed might be a tad more difficult.
Yes. I meant voltage.

Well... I figured I could use a wire in a way other than originally designed... But Why can't I add a wire to the existing magneto?

Here are more photos in case that helps.

image_7.jpeg image_8.jpeg image.jpeg image_1.jpeg image_2.jpeg
 

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Discussion Starter #5
and some more photos.

image_3.jpeg image_4.jpeg image_5.jpeg image.jpeg
 

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Well... I figured I could use a wire in a way other than originally designed... But Why can't I add a wire to the existing magneto?
Well of course you can......IF you know what you are doing.

Often there are two mag outputs: one for power to the lights and the other being a high voltage for the ignition.

It probably would be better to get power from the headlight or tail light; something that is ON all the time.

Note: I'm not really looking at your pictures.
 

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Discussion Starter #7 (Edited)
Well of course you can......IF you know what you are doing.

Often there are two mag outputs: one for power to the lights and the other being a high voltage for the ignition.

It probably would be better to get power from the headlight or tail light; something that is ON all the time.

Note: I'm not really looking at your pictures.
Duly noted. I will be taking another look at it soon.
 

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Discussion Starter #8
It's a pretty big decision though. Because wiring an assembled vespa is not an easy task... compared to other bikes.

It's do-able, but we really have to make sure re-wiring is 100% necessary before we do it. Hence why I've made this thread.
 

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Well maybe a little more detail is necessary.

At the brake light switch, one wire goes to the brake light bulb, then through the bulb to ground (another wire or frame ground).
You can check that wire run with an ohm meter. You can also check the bulb with a meter.

Then the other wire at the switch is the "hot" wire and it should have voltage when the engine is running.
If that voltage is missing, then you need to trace it back to the mag or a fuse or connection point.
Not knowing where that connection point is supposed to be makes it a bit more difficult.
 

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Well maybe a little more detail is necessary.

At the brake light switch, one wire goes to the brake light bulb, then through the bulb to ground (another wire or frame ground).
You can check that wire run with an ohm meter. You can also check the bulb with a meter.

Then the other wire at the switch is the "hot" wire and it should have voltage when the engine is running.
If that voltage is missing, then you need to trace it back to the mag or a fuse or connection point.
Not knowing where that connection point is supposed to be makes it a bit more difficult.
Ya. Well the diagram shows which wire goes to which coil in the alternator.

The photos should show which are ACTUALLY going to the alternator.

Anything I can do that'd get you to actually look at the photos? Pretty please?
 

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Anything I can do that'd get you to actually look at the photos? Pretty please?
If I was getting paid by the hour for fixing this problem, I would look at whatever you wanted.
Alas, I'm not and you have posted, what, a dozen pictures.

It is only ONE wire. While I haven't worked on a Vespa in a long, LONG time I think you are making this MUCH harder than it IS.
 

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Anything I can do that'd get you to actually look at the photos? Pretty please?
If I was getting paid by the hour for fixing this problem, I would look at whatever you wanted.
Alas, I'm not and you have posted, what, a dozen pictures.

It is only ONE wire. While I haven't worked on a Vespa in a long, LONG time I think you are making this MUCH harder than it IS.

[OK I looked at the 3 most recent ones. As I suspected, I can tell NOTHING useful from them.]
 

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Discussion Starter #13
If I was getting paid by the hour for fixing this problem, I would look at whatever you wanted.
You know this world is a messed up place when you can earn the title "Super Moderator" without earning a single red cent, eh?

All due respect, Reed J

P.S. It's still a lot more complicated than you think. :p
 

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BASIC Black wire is ground,,, there is NO voltage until bike is running,,FOR this to work You need to power up the brake switch-( yellow wire or ?? blue wire )----THE OTHER SIDE OF THE THE SWITCH WIRE HAS TO GO DIRECTLY TO THE BRAKE LIGHT BULB-----when you depress the brake lever the power ( voltage goes to the bulb ) as the other side of the bulb is grounded it will light up========therefore as per your diagram connect take the black wire from switch & hook it to the blue wire to ONLY the BULB (sever the connection to ground ON THIS SWITCH wire) assuming the blue wire has a DC voltage with bike running,,,IF not then hook up the blue from switch to yellow from mag
 

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Discussion Starter #15
UPDATE:

This ended up being a two part problem.

The old housing unit for the bulb wasn't making good enough contact

One of the tail light mounting bolts was grounding out the circuit. Solution: rubber gromet.

It was solved quite some time ago, but I haven't had time to reply until now.
 

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Thanks for reporting back.
It really wasn't as complicated as you imagined, now was it ? :cool:
 

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Poor contact to frame ground...believable. rubber grommet to isolate from ground....unbelievable. Someone mentioned looking for DC voltage on this machine... Aint gonna happen.
 

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Well as long as you didn't cut the red wire....or was it the green?...:mrgreen:
 
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