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Old 03-13-2010, 02:39 PM
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Quick Questions on Alt.

I have a Delco Remy 100 amp Alt. and I have a few quick questions about the wiring.
The sensing wire (2)... Can I run a jumper from the battery post on the rear of the Alt and forget about it or should I run a constant 12v source from further away?
The Ign. Wire (1)... This should be a 12v switched source correct? If I use a 16ga wire and solder that to the brown wire (thin wire) will that work? Do I need a specific resistance?
Sorry for the Newb questions.
Rich
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Old 03-14-2010, 02:22 PM
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The sense wire will work fine when jumped to the BAT terminal, but may work more accurately if you connect it closer to your fuse box or wherever the original wiring was connected. Its designed to sense the reduced voltage created by load, and in old wiring some of the voltage reduction may be simple resistance. When connected to BAT it is simply sensing the current battery voltage at the closest point to the battery.

The other terminal wire should go to a switched source, either connected through an indicator light, or through a resistor (about 10-20 ohms should work). 16 gauge wire will work fine.

If you connect terminal 1 to a switched source without a light or resistor in the line, you may not be able to shut your car off because the running alternator will back-feed power to the ignition. In some cars you also need to use a diode that makes the current flow only one-way (from switched to the alternator) on this wire.

Bruce
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Old 03-14-2010, 07:57 PM
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Quote:
Originally Posted by 75gmck25
The sense wire will work fine when jumped to the BAT terminal, but may work more accurately if you connect it closer to your fuse box or wherever the original wiring was connected. Its designed to sense the reduced voltage created by load, and in old wiring some of the voltage reduction may be simple resistance. When connected to BAT it is simply sensing the current battery voltage at the closest point to the battery.

The other terminal wire should go to a switched source, either connected through an indicator light, or through a resistor (about 10-20 ohms should work). 16 gauge wire will work fine.

If you connect terminal 1 to a switched source without a light or resistor in the line, you may not be able to shut your car off because the running alternator will back-feed power to the ignition. In some cars you also need to use a diode that makes the current flow only one-way (from switched to the alternator) on this wire.

Bruce
Great info, thank you. I did go out and purchase a couple diodes... p/n: 276-1143... to help prevent that BUT, I don't know which way to install There is two in a package, they are taped together one end being white tape and the other end being red tap... . This is Definitely a learning curve for me. Every bit of information is knowledge for my empty well of a brain.
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Old 03-14-2010, 08:11 PM
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I am no expert on diodes. However, if one end has a colored stripe on it, that should be the cathode end.

The diode will allow current to flow toward the cathode (color banded end), so that end should be toward the alternator, and the other end goes to the ignition switch.

That way the alternator cannot directly provide power to run the ignition when the switch is off.

I found some additional info online that seems to indicate there should be a silver bar on the cathode end. There is no mention of a red bar on the diode.

Bruce

Last edited by 75gmck25; 03-14-2010 at 08:20 PM.
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Old 03-14-2010, 10:43 PM
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Quote:
Originally Posted by 75gmck25
I am no expert on diodes. However, if one end has a colored stripe on it, that should be the cathode end.

The diode will allow current to flow toward the cathode (color banded end), so that end should be toward the alternator, and the other end goes to the ignition switch.

That way the alternator cannot directly provide power to run the ignition when the switch is off.

I found some additional info online that seems to indicate there should be a silver bar on the cathode end. There is no mention of a red bar on the diode.

Bruce
I went back out to the garage and looked at the diode... there is a silver "ring" at one end...
I imagine the best thing to do would be to solder this diode to the 16ga wire and then shrink wrap and tape over with rubber electrical tape and then she should be a done deal correct?
I truly appreciate your assistance.
Wait...... Side thought here: How will I know if the diode is installed incorrectly? Even if I have a separate 12 volt switched source to the alternator can it still back feed?
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Old 03-15-2010, 07:11 AM
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Quote:
Originally Posted by AMC Lives
I went back out to the garage and looked at the diode... there is a silver "ring" at one end...
I imagine the best thing to do would be to solder this diode to the 16ga wire and then shrink wrap and tape over with rubber electrical tape and then she should be a done deal correct?
I truly appreciate your assistance.
Wait...... Side thought here: How will I know if the diode is installed incorrectly? Even if I have a separate 12 volt switched source to the alternator can it still back feed?
The banded end towards the alternator. If you install it backwards it wont work at all as it will prevent the voltage getting to the alternator on pin 1. Consider it a one way valve for electricity, current can flow from the non banded end to the banded end but not the other way so when you turn the key off it cant back feed.
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Old 03-15-2010, 09:52 AM
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