Hello
My Yamaha 1vj doesn´t charge its battery. Lights work ok. I measured the generator coils ohms and seems to be ok 1,2 ohms. I took this values measuring between the white cables that comes form the generator to the rectifier-regulator.
When the motor is idling i can measure 13,3v on the battery but when the lights are on, goes to 11,3 (that is the voltage in the battery when the motor in not running. Battery is not full charged). if I increase the RPM to 3000 the Volts remains the same. What´s your opinion? should I replace the rectifier or could be a generator problem? Thanks for your help!!

First you must find the voltage regulator under the seat. It will have three white wires and one red. Make sure the regulator has a good ground to the frame.

The 3 white wires are the 3 AC output wires from the alternator.They are all white, so for this test, let's call them X,Y,Z.
Set your meter to AC volts and while the engine is running, measure between X&Z, X&Y and Z&Y (probe the back of the plug). You should measure the same voltage, in each case between 10 and 18 volt AC. If you pass this test then your alternator is fine.

Plug the regulator back in circuit. Then set your meter to DC volts and test between the red wire (probe the back of the plug) and negative of battery with the engine running. Your reading should be over 14v. If not, regulator is faulty.

If you pass the second test, then the fault is a fuse, faulty ignition switch or some other wiring fault.

Fancy doing some tutorials Dave? open an Electrics/Wiring Section in the Nuts & Bolts.

Mezo.

Yes , Dave, just great!
Olli

Ive set two more sections in the workshop, Intake (carbs etc) and Electrical.

When you get a min Dave post something like this & ill sticky the post, easier to point a member to some basic Info/checks before they ask "my bikes not changing"

Mwz.

Thanks to all for your comments!!! I will do the voltage today, I hope that the problem remains in the rectifier-regulator!!

Hi, you can also unplug the regulator and measure the open circuit voltage from the stator (the 3 white wires) from memory I think it is about 18 Vac at idle to about 70 Vac when you rev it up. The voltages should be about the same across all three windings.
Regards, Dave

Yeah.....what I said 5 posts earlier!

ActionManMelb wrote:Yeah.....what I said 5 posts earlier!

Yeh I know Dave, but it isolates it from the load of the regulator and battery etc.

"Touché"

M.