Alternator charging light

[Morris]

Seems to me that if you have the one wire alternator...you could take a jumper off the alternator and go to one side of a lamp.....then on the other side of the lamp...connect to the battery......that way when you turned the ignition on you would see the lamp on from one side being hot ...then when the alternator started spinning and had a output the light would go off because you would have a 12 volt potential on both sides of the lamp....if the alternator started going bad the the battery side would be hot and the alternator side would be ground so the lamp would light.......I think ��

[jhv48]

Or, you could watch your ammeter and if it stays to the left of center, you probably have an alternator going bad.

[Gaz64]

Originally Posted by Morris

Seems to me that if you have the one wire alternator...you could take a jumper off the alternator and go to one side of a lamp.....then on the other side of the lamp...connect to the battery......that way when you turned the ignition on you would see the lamp on from one side being hot ...then when the alternator started spinning and had a output the light would go off because you would have a 12 volt potential on both sides of the lamp....if the alternator started going bad the the battery side would be hot and the alternator side would be ground so the lamp would light.......I think ��

Yes, that should work.
A bulb in parallel with the heavy lead, would show up any voltage difference, so brightest at ignition on, 12v + on one side, and 0 volts at the alternator.

The bulb would present virtually no circuit path while in parallel with near 0 ohms of the heavy charging wire.

[patrickt]

I don't think that will work -- but I have never tried it, so I really don't know. But if it was that easy, why would Tuff Stuff go to the trouble of putting this in the instructions for its 1-wire alternator?

NO WARNING LIGHT
Note that a 1-wire alternator does NOT permit the use of a charge
warning (idiot) light. Most hot rodders and muscle car enthusiasts
prefer the use of a volt meter or ammeter to monitor charging.
However, certain Tuff Stuff alternators like the 7127, 7139 and
7140 series have terminals that may be used for a warning light.
To wire a warning light using one of these alternators, simply
remove the terminal plug cover and connect the R (Left terminal,
looking from the back of the alternator) to the warning light wire.
https://www.tuffstuffperformance.com...structions.pdf

and PowerMaster says the same thing about theirs:
https://www.powermastermotorsports.com/001___IS_ALT.pdf

[Boise]

Originally Posted by patrickt

I don't think that will work -- but I have never tried it, so I really don't know. But if it was that easy, why would Tuff Stuff go to the trouble of putting this in the instructions for its 1-wire alternator?

NO WARNING LIGHT
Note that a 1-wire alternator does NOT permit the use of a charge
warning (idiot) light. Most hot rodders and muscle car enthusiasts
prefer the use of a volt meter or ammeter to monitor charging.
However, certain Tuff Stuff alternators like the 7127, 7139 and
7140 series have terminals that may be used for a warning light.
To wire a warning light using one of these alternators, simply
remove the terminal plug cover and connect the R (Left terminal,
looking from the back of the alternator) to the warning light wire.
https://www.tuffstuffperformance.com...structions.pdf

and PowerMaster says the same thing about theirs:
https://www.powermastermotorsports.com/001___IS_ALT.pdf

The one wire alternator can be used with a functioning warning light!

So after looking around and taking some readings using the meter I figured it out. My alternator is a one wire version. The stator and field connections were unused and covered with a rubber cap. I found the black wire coming down to the alternator in the harness but still unconnected. I connected this to one of the alternator connections. Then I verified that the voltage regulator was no longer used. I had to jump the solid black and solid blue wires that go to the voltage regulator.
After that the alternator warning light works perfect! Its an easy job and works for anyone who has a single wire alternator.
Thanks for all the help

[patrickt]

Originally Posted by Boise

Thanks for all the help

... and they all lived happily ever after.