Yamaha G9 Voltage Regulator Wiring

[Harbormike]

I have a 1995 Yamaha G9-AM gas golf cart. It has been eating batteries. I have replaced 3 batteries in the 3 years I have owned it. I have replaced the voltage regulator. It ate another battery during the July 4th holiday. It runs fine until it is run for several hours continuously. I took the wiring harness off to check it and every wire is in good shape. I used the "Wiring diagram for G9" to be sure I reconnected everything correctly. I discovered that the brown wire from the voltage regulator to the F2 terminal of the starter generator was missing. There wasn't a terminal in the plug going to the VR. Am I using the right diagram and should the brown wire on the diagram be there and connected? Thanks for your help.

[firemedic247]

I did a clone swap and completely rewired my G9. Here is my wire diagram I came up with using a stock G9 4 wire voltage regulator. If you switch to a 3 wire you can just eliminate the brown wire from the diagram.

[cgtech]

Originally Posted by firemedic247

I did a clone swap and completely rewired my G9. Here is my wire diagram I came up with using a stock G9 4 wire voltage regulator. If you switch to a 3 wire you can just eliminate the brown wire from the diagram.

I do not think this is correct, if you remove the B+ from the 3 wire mechaincal regulator, it doesnt work.

[firemedic247]

Please correct me if I'm wrong but from what I under stand this is how you wire a 3 terminal voltage regulate to a G2 system

D- should go to Ground
DF should go the green wire (input to S/G)
D+ should go to the red wire (Output from S/G)

A G9 V/R has 4 terminals and the 4th terminal is connected to F2 side of the solenoid by the brown wire. So if you switch to a 3 Terminal V/R you should eliminate the brown wire and everything will still work.

[cgtech]

I believe D+ is "12v +" whenever key is on. D- is "12v -". F goes to the green small wire on generator. Small red wire is "12v+" whenever key is on.

[Harbormike]

Thank all of you. My question is answered that the brown wire should go from the 4-terminal automatic voltage regulator to the F2 terminal on the S/G. I can also swap to an older adjustable regulator and not use the brown wire. I am guessing someone changed it back to the old style VR on my cart and then put the new style automatic VR back in, but forgot to reinstall the brown wire. I will keep it stock and add the brown wire. Thanks again for the help!

[dzig_33]

So, was it always outputting a high fixed voltage, or is it something else ruining the battery. I have hooked up a voltmeter to my cart, and it always outputting high 15 volts, running fast or slow, battery fully charged or down some after leaving radio on without running for a while. Does this seem normal, or should it charge at 12-13 volts after the battery is up?

[bigstik40]

Originally Posted by dzig_33

So, was it always outputting a high fixed voltage, or is it something else ruining the battery. I have hooked up a voltmeter to my cart, and it always outputting high 15 volts, running fast or slow, battery fully charged or down some after leaving radio on without running for a while. Does this seem normal, or should it charge at 12-13 volts after the battery is up?

Voltage at the battery per Yamaha service manual should be 14.5 - 15.5 volts at elevated RPM (1/2 throttle or so). The older mechanical regulator is adjustable. - RAY

[Harbormike]

With the brown wire missing the solid state voltage regulator basically doesn't regulate the voltage and the battery gets charged at over 15.5, near 16 voltages. When the cart is run at high rpm for a continuous period of time, the high voltage causes the battery to boil and degrades the litholyte to the point the battery can no longer hold a charge.
I understand that the brown wire from the F2 terminal of the starter generator to the voltage regulator supplies the voltage signal to the solid state regulator that tells it how much to reduce the voltage charging the battery. Without it, the voltage regulator supplies full generator voltage (over 15.5 volts) to the battery with the motor running at high rpm, ruining the battery. It took me three ruined batteries and a close look at the electrical diagram to figure out what was wrong.