Newbie with battery charging question

[Bikerndiver]

The battery in my buggy is not charging. I went to a local mechanic and with the buggy running, he tested the battery and said it was good. However, the alternator (internal regulator) was only putting out 12.3 volts....

I know I need some idiot light to come on to get the alternator to work. I seem to have that light (incandescent) wired into a bracket at the rear of the motor. Dumb place, but that's where the PO placed it....

Anyway, the light has two wires coming off it, a green and a red. The red wire goes to a terminal on the coil. The green wire goes up, and is attached to a black wire that goes into a wire loom....from there, I have no idea where it goes.

I looked at my alternator and saw a large red wire that goes to the battery/starter. There is another terminal on top of the alternator, but that has nothing attached to it.

When I start the buggy, the idiot light, described above comes on and stays on, no matter what RPM the motor is running at. I have a voltage gauge in the dash and the needle barely comes off of 12 volts even when I'm revving the motor.

I'm not sure what my next step should be to diagnose the no charge issue. I'm also confused by my idiot light being wired to the coil. Seem like everything I've read says the light should come off the small terminal on top of the alternator.

Any help is appreciated.
Thanks!
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1966 Manx clone (possibly a Joe Poty Enterprises) named SANDY. '70 to '73 1300 cc w/1600 DP heads, twin carbs and headers

[slayer61]

The small term on the alt. needs to be connected to your idiot light.
First... verify that one side of the idiot light is connected to the + side of the coil.
Then, connect the other side of the idiot light to the small terminal on the alternator...
Lastly... test. Turn the key on. Verify that the idiot light comes on. If it does... you're halfway there. Start the car. The idiot light should go out. If it does... You're charging your battery! If it doesn't go out... you have more "fixing" to do


ETA welcome to the wonderful world of "previous owners" AKA POs!
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[OCD Garage]

...and if you start the car, the light goes out, it starts charging but you can't turn the it off from the ignition key, it means the 'now' working alternator is back feeding to the coil. The cure would be to add a diode in the line or give the light (+) power from a different switched source.

You didn't mention it either way, but I assume you bought a running buggy without being aware of the charging problem? That set-up doesn't sound correct to me, does the bulb light when you ground the wire not attached to the coil? The light works by getting 12v on one wire and the other provides (-) through the diode trio/regulator circuit until the alternator spins up, then that point also becomes (+) so without a ground, the light goes out until an internal diode leaks or otherwise breaks down. If your alterator brushes are too short, it won't charge and the light may not work without the connection through the rotor, through the regulator back to ground, as well.

[Bikerndiver]

[Dale M.]

14 Volts (+/- about 1/2 volt) is good.... For instrumentation a volt meter on dash will show condition of charging system any time you glance at it.....BUT you still need idiot light to initialize alternator on engine start up...

For headlight upgrade I went to halogens, made a great difference, but they have been surpassed by LED, but expensive....
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“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.

"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[DeathBySnuSnu]

[jspbtown]

Maybe too obvious but...internally or externally regulated alternator?