Re: alternator conversion draining battery.

Posted by Jon Hagen on May 26, 2007 at 07:56:20 from (75.104.57.1):

In Reply to: Re: alternator conversion draining battery. posted by Randy in SW Pa on May 26, 2007 at 04:07:42:

" have a delco alternator. There is one bigger post in the back of it. and a white clip in the side with 2 wires in it. A red one and a smaller white one. The red one in the clip is connected inline to the bigger post in the back, and then gos to the starter. Then the smaller white one goes to the positive post on the battery.

For the on and off switch I have a wire from the starter going to a toggle switch then to some resistor gizmo for the 6-12 volt conversion, and then to the coil. I dont know why it is hooked up this way but at the time it seemed to work and I just left it."

Ok Randy, the small white wire is the #1 exciter wire. It must not be connected to the battery post as it will be powered all the time and discharge your battery. The little white wire must be connected to the ignition switch terminal that goes to the ignition resistor. This will connect power to the white wire to start the alternator charging when the ignition switch is on, yet disconnect it from power when you turn off the ignition,which is how it must be to prevent the battery discharge.
Your other wiring sounds OK, except the output from the alternator should go to the ammeter first with another wire from the other ammeter post to the starter/battery so the ammeter can give you an indication of charge/discharge.

The wire from the alternator output (BAT) terminal, along with the wires that feed the ignition and light switch must be on one ammeter post, with only the wire to the starter/battery being connected to the other ammeter post. If the ammeter reads in reverse, exchange all wires to the opposite meter post.

If by chance your engine continues running with the ignition switch off after connecting the white alternator wire to the ignition switch, you may need to add a device in the white wire to prevent a backflow of power from the alternator to the ignition switch.
This can be a diode as Old suggested, or a resistor or indicator light which is a form of resistor. I perfer the indicator light, as it gives a visual indication of power getting to the alternator exciter circuit and a replacement is avalible at any hardware/auto parts/farm store or gas station. A two wire gen or oil light from a junked car or the front side marker lamp socket from a 70's Ford works well. Just connect the two socket wires to the two cut off ends of the white wire somewhere between the ignition switch and alternator.
This little light will prevent backfeed from the alternator reaching the ignition coil and causing it to run with the ignition switch off.
The light will also indicate alternator condition. With the ignition on but engine not started, the glowing light indicates that the alternator exciter circuit is getting power as it should. If the light glows with the engine running fast, then it indicates a problem with the alternator.

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