Modern Vespa

Hello,

Please refer to this diagram for my question:

https://www.scooterhelp.com/electrics/pages/VB1T.150.html

There is a yellow wire coming from bottom left coil and then connects to the green wire (from bottom right coil) at the distributor. From here, we have two yellows wires running to the front and to the rectifier.

The question is what is the purpose of this yellow wire (coming from the bottom left coil) and what voltage should it have when the engine runs?

When the engine runs, I measure AC voltage of the green and yellow wires individually and the result is 6V from the green one and only 200mV from the yellow one. I expect to have 6V too from the yellow one since it should carry the voltage from that coil.

Please help.

If you have the stator as per that diagram, then yes, you should get the same output from both those coils. Check the resistance to earth of both, should be exactly the same.

Thank you so much for your info. So I measured the resistance between the green wire and engine body, it was 1.2 ohms and for the yellow wire, it was 0.6 ohms. Next step I will remove the coils off the stator plate and measure them directly. Sounds like I will need a new coil. Thanks again Sir.