Modern Vespa

I've been trying to sort out electrical issues on a 6 volt (no battery) 1965 VBB that I completely rewired. Everything electrical on the scooter is new.

I have a question about the horn. Seems like it should be one of the simplest circuits to figure out on the scooter but my horn won't toot.

I disconnected the green wires at the junction block and tested the green wire for continuity between the junction block and the handlebar switch and between the switch and the horn. I have continuity.

Next - with the green wires still disconnected at the junction block and with the engine running I checked the voltage between the green wire from the stator and the engine case. No voltage registered on my multimeter. Was my technique a valid test procedure for the green wire? Is there another procedure I should try to figure out why the horn won't work?

Where were you testing the green wire output, at the junction box or directly off the stator? It sounds like either the coil is bad, or you have a short in the wire between the coil and junction box, or, the green wire isn't connected to the coil, or, there is a break in the green wire between the coil and junction box. Did you check the continuity between the junction box and coil?

If it were mine, I'd try temporarily swapping the green for either the yellow or blue at the junction box. And, I'd check the continuity of the green coil itself.

Are you sure it's an AC horn?

http://www.scooterhelp.com/tips/parts/horn.main.html

does the headlight work?

if so, the horn should work. they are powered off the same coil.

ignore the advice about swapping with the yellow and/or blue wires. that won't work, and will cause nothing but issues.

1. The horn is new 6 volt AC

2. I tested the voltage of green wire from the stator at the junction block. I'll pull the flywheel and check for continuity of the green wire between the stator and the junction block as soon as I get a chance.

3. The headlight does NOT work. I read an earlier post that indicated that the green wire is also part of the headlight circuit which was why I was attempting to test the voltage of the green wire.

4. Is connecting one lead of the multimeter to the green wire and the other lead to ground while the engine is running the correct way to test the coil? If not, what is the correct procedure for testing it?

Thanks

Multimeters don't always give good AC voltage readings from stator coils because they don't load the circuit. A test lamp works better.

You can use the headlight as a tester.

Buy (or make) a long test lead with alligator clips at both ends.

Disconnect the green wire at the junction box. Clip one end of the lead to the green wire coming from the stator, and the other end directly to the headlight. If the stator's good, the headlight should light with the engine running.