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Wayne S.
Wayne S., Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 1255
Experience:  Experienced and Licensed Motorcycle Mechanic - all sizes and brands welcome.
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I have a 1979 Vespa P200E. All was working well until recently

Customer Question

I have a 1979 Vespa P200E. All was working well until recently I noticed the junction box and coil pack had many frayed wires. I electric taped them as well as possible and replaced the coil pack since the ground had broken off. Now the headlight does not work, nor the horn. However, if I push the horn button the headlight works! (and the horn tries, but does not get enough juice with the light taking most all. What have I done wrong??
Turn signals & brake light works fine.
Submitted: 2 years ago.
Category: Motorcycle
Expert:  Wayne S. replied 2 years ago.
Hi, the wiring colors were changed around 1979 so you have either alot of yellow wires or some pink and purples. Swapping the pink and purple wires on the junction might fix your problem.It sounds like the horn power is diverting to the headlight.Might help if you can list the colors on your junction so thepower can be traced according to wire color. Let me know that if you can or if swapping the wires changes anything.---
Customer: replied 2 years ago.
Yes, from the junction box red, yellow, purple and black wires all go into the flywheel magneto. Then out of the magneto come white, red and green wires, which go into three of the four slots on the coil pack. The other slot on the coil pack is also green and goes directly through the junction box - apparently as the spark plug power to the switches in the front of the vehicle.
I've been careful to keep the wires in the junction box as I found them, and don't want to begin to switch those. So the only options I see to switch would be the white/red/green that come from the magneto and go into the coil pack. But their colors seem to match the color required as stamped on the coil pack. That's why I'm stumped. I will try switching and let you know what happens.
I also have a separate brown/black two wire harness that comes from the front of the engine. I THINK it is for a neutral switch that seems to no longer exist on the vespa. When I connect the two wires together, the neutral switch stays on, despite the gear, so I have bought a new neutral switch but am unsure how to connect to see if that puts the neutral switch working properly. Or - are these wires that have something to do with the horn or light? - I don't think so.?
Again, I'll try some switching today and see what happens. Thank you for your communication.
I downloaded a color-coded wiring diagram for the vespa P200E (VSX1T) off the internet and it has been helpful to a point, but also very confusing. If you don't have it, you might download the same and see what I'm dealing with.
THANKS, Craig in Santa Barbara, CA
Customer: replied 2 years ago.
When i connect the brown/black wires the neutral LIGHT stays on. I want to see if connecting my new neutral switch (somewhere?) will cause the LIGHT to work properly when the clutch is only in neutral. Hopefully this clarifies what I posted less clearly before.
Customer: replied 2 years ago.
OK - I switched different combos of wires in the junction box with NO CHANGE - meaning, tail light & turn signals still work and horn and head light don't. Coming out of the magneto, the white wire is carefully plugged into the place marked for white on the coil, and the same for the red and green wires. The primary mystery - and clue for you, is that when I push and hold the horn button the headlight works fine - both high and low beams; and the horn tries to sound (low murmuring), but can't receive enough juice with the headlight sucking most all of it. It sure seems to me that some wires must be crossing somewhere to cause that. Any more ideas?
Expert:  Wayne S. replied 2 years ago.
Sorry, I usually just work here later on in the day. I see you were posting earlier about your bike.
I would suggest if the wiring diagram matches your bike that you follow the individual circuits like the horn circuit and verify that all it's connections match the wiring diagram. If anything odd shows up then
those wires might be for another circuit.
The wiring can sometimes have the same color but be for a different circuit. Also, sometimes circuits can be made through the ground system.
For example, the headlights could be grounding through the horn or vice versa. It may take awhile to sort out the circuits.
I checked the wiring diagram and it seems like your headlight might be grounding through the horn circuit when you press the horn button.
The horn button acts as a ground for the horn but is also grounding the headlight. Check if the headlight works with a separate ground attached.
The headlight maybe getting some power backwards through the horn
or something odd anyway. I would make sure the headlight has power
coming from the regulator on the purple wire to the headlight switch.
You might try disconnecting the horn and then get the headlight working
on it's own first. Then reconnect the horn and check it's circuits later.
Let me know if any of that works.
Thanks, WS
Customer: replied 2 years ago.
HI Wayne - I appreciate your thoughts, but for me, I don't find it personally helpful. I have followed the electrical diagram as best as I can, but it mostly confuses me. I'm not even sure how to attach a separate ground to the headlamp. And getting power "backwards" doesn't compute to me either. I know your are doing what you can with what I'm giving you - but honestly I'm sorry I sent $29 for help at this point. I was first given the option of $5 down, but then that option was taken away when I chose to pay by PayPal. Is there any option of a refund? Or can you be more specific on what a willing "hands on" guy but not an electrician or "tech" guy can do? I'm not angry - just frustrated.
Expert:  Wayne S. replied 2 years ago.
Hi, no problem, you can request a refund or we can just try a few tests
and try to simplify where possible.
My idea is to just disconnect the horn if necessary and work on getting the light operating as they should operate even without the horn being
hooked up at all.
There is a purple wire on the regulator that is where the lights are
supposed to be getting their power from to operate.
If you look at the dimmer switch it should have a purple wire
entering there. That should have voltage with the bike running and
lights on. If so the lights can be fixed one way or another.
The horn circuits can be checked later.
Let me know, or email just answers for a refund if preferable.
Customer: replied 2 years ago.
OK - I'll disconnect the horn and try to get the headlight working independently - good strategy. We'll see if I can find a way to get the light working. I'll probably get to that tomorrow, on Saturday, and get back to you with my report. Thanks.
Expert:  Wayne S. replied 2 years ago.
Okay, let me know what you find and we can go from there later.
(no reply necessary)