How do you test a voltage regulator?

[Beachrights]

And had it load tested today to be sure- funny thing is it is rated at 550 and tested 620!

[smallblock450sl]

Originally Posted by Beachrights

Smallblock- Good info! Couple of questions- Are you saying put meter on both red and green wires at the same time, meaning positive, negative probes or each individually and ground? >Just read the ohms of the red and green leads out of the starter/generator.

Black wire? Do you mean starter blackwire to battery? Or voltage regulator? >Just make shure there is 12 volts negative at the black wire at the voltage regulator plug in connector.

cart will run for about 20 minutes before a no start- slow spin.

battery is new- also have swapped a known good one.

That's a bummer!

[Beachrights]

If it was a horse I would have shot it already!

[tcb2020]

when you say first and third terminal there are only three there are two on top on each other and then a third wire which two need to be jumped together?

[kantuckian]

Good Info Thanks

[Dave Marsh]

My Yamaha G9 limo I bought used was overcharging and boiling the water out of the battery. I tried two new Yamaha style voltage regulators that just plug in. Had no luck at all. I don't know the history of this cart but suspect the wires had been switched around in the plug. I was just blowing fuses or when I moved the wires around in plug like I thought they should be from a wiring diagram, it would just do what it did before and charge at 18-19 volts. I finally bought a voltage regulator for an EZ-GO golf cart that had the Red, Black and Green wires coming out of it. Used the EZ-GO diagram to wire it and everything started working like it should. It went to 14 volts while running and not over. I feel you can't go wrong when you have colors to match. The issue with the Yamaha style voltage regulator is no matter how hard I searched the internet I could not find a picture of where each wire was to plug in when you are looking at the voltage regulator. I may of had bad voltage regulators or I damaged them right off the bat when I plugged them in. But after buying two of the Yamaha style voltage regulator with no luck, I thought I would go this way and it worked for me. While I was working on the charging system I also replaced the brushes in the starter/generator, they where ready to be replaced and I'm glad I did it. They were worn down so much that they weren't making good contact.

[sho305]

With a generator the VR just runs current through the field (the small wires or wire) to make it charge when it wants to. Some generators one of the wires is connected inside the gen, with a yamaha they are not and both come out the side. When you test either the VR is grounding the one wire and other has 12v, or its powering one wire and the other is ground. The Vr just completes the circuit so the field is powered. You can figure the wires out out by how they told you to test. If you hot wire that circuit and connect it like the Vr does, start the cart for a moment, you should see ~15v at the battery as it will be fully charging. Though generators only make max power at higher rpm it may not at idle speeds. If you don't then the gen or wiring has a problem. If you look at a wiring diagram you will see the gen field go to the VR and the other will go to power or ground the opposite of what the VR connects to.

If I see it right the green wire grounded makes it charge, means the VR is grounding it to charge. The other field wire should go to 12v.

Also check the other wires to the VR for connection issues, if the VR can't see what the battery is at it can't control the charging properly.