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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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78 Vespa Piaggio P200E - Headlight is dim and turn signals

Customer Question

78 Vespa Piaggio P200E - Headlight is dim and turn signals don't function right. Has new rectifier and battery. New headlight and turn signal bulbs.
Submitted: 2 years ago.
Category: Motorcycle
Expert:  Wayne S. replied 2 years ago.


Can you get me a voltage reading off the battery when
it is not running and also when it is running at a fast
idle. Are the signals all working but not blinking?
Thanks, Customer
Customer: replied 2 years ago.
12 Volts both readings
Expert:  Wayne S. replied 2 years ago.
Sounds like it is not charging the battery.
Could be a faulty stator but also
check the fuse for poor connections.
Check the junction box where all the wires
meet near the engine. Clean any place on
the frame where you have ground wires.
Clean and check the battery ground.
Do you have battery voltage on the rectifier
grey wire?
Customer: replied 2 years ago.
grey wire has voltage
Expert:  Wayne S. replied 2 years ago.
If you have these colors on your rectifier/regulator
check them with your multimeter set on AC volts.
Two purple wires and one yellow wire.
See if you can get a voltage reading off these and
try it with the engine running fast idle or more
when you take the reading.
Let me know what AC volt readings you get, no rush,
just come back here when you are done. Thanks
Customer: replied 2 years ago.
6 to 10 volts
Expert:  Wayne S. replied 2 years ago.
Your AC voltage is much too low to charge the battery.
The yellow wire should read around battery voltage
at idle but can go as high as 50 volts AC when the
engine is at high speed.
I would check each of those wires along their length
back to the stator on the engine.
If you have the junction box check the wires there carefully.
The outer purple wire may just go back to the ignition
switch but the inner one goes to the stator as well as
the yellow. These are both connected to a stator coil
which should be putting out much more than a charged battery.
You may just have a bad wire or bad ground on the engine
but if not the stator coils will have to be removed checked out
and possibly repaired or replaced.
Expert:  Wayne S. replied 2 years ago.
The outer purple wire on the rectifier actually goes to the
lights but the other purple and yellow are charging
wires from the stator. Grey is battery, black is ground.
The stator wires need to put out enough voltage
so once it is rectified it is enough to charge the battery.

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