Need alternator wiring help

[jmgtp]

This is for my LX9 swapped Grand Prix which keeps frying alternators.
They last a few days or less. This last one went about 10 miles before death.

The dohc motor used a 2 wire connector on the alternator but the new alternator that I have for the LX9 uses the newer style, 1 wire. I'm using a 3100 lumina alternator bracket and a CS130 alternator. I had 2 wires to chose from to connect to the 1 wire connector for the new alternator. I believe I may have spliced the 2 wires together and connected to terminal L on the new alternator but I don't know for sure till I pull the harness apart.

But this should be simple.
1) is terminal L the correct one to supply voltage to in order to turn the alternator 'on' (aka generate the field)?
2) if my #1 assumption is correct then as long as I have 12v that is switched with the ignition connected to terminal L, the alterantor should turn on and there is no reason to believe the alternator failures are wiring related

My only other thought is that the battery is an old Optima Red Top. It died BAD over the winter. I nursed it back with a Battery Tender Plus charger and it lives again. It starts the car every morning but if I let the car sit for a week it will be dead. Could the battery actually be killing the alternators? I don't see it, especially since they seem to die within a day!

[neophile_17]

If I remember correctly you need a bulb (dash light) or resistor between 12V and terminal L. HTH

~sam

[TechRod]

If I remember correctly you need a bulb (dash light) or resistor between 12V and terminal L. HTH

~sam

X2, I just went through this.

[jmgtp]

THANK YOU.

I did some reading (http://www.alternatorparts.com/cs130_sbpage1.htm) and I was nearly at the same conclusion that you both have arrived at.

It kinda clicked when I realized that I was NOT getting an idiot light in the dash when the alternator failed, I just happened to notice that the volt gauge read very low. In the past, if the alternator failed, the 'check gauges' signal would illuminate in the heads up display.

Now, I'm fairly confident that I have the L terminal wired incorrectly. I'm having my dad, an electrical engineer, come over tomorrow to go over it with me.

[TechRod]

I wired mine as shown here.

[jmgtp]

Interesting, I was wondering if anyone ever took advantage of the voltage sensing circuit. Does the red 'box' on the wire to pin L represent a resistor? If so what value did you use? In the link I posted above with the CS130 info, I read a 35 - 150 Ohm would work.

[TechRod]

You only need the resistor if you're not wiring it up to the dummy light, otherwise the bulb provides the necessary resistance.

[jmgtp]

Makes perfect sense - and my lack of an idiot light illuminating when it failed alludes to me not using the correct wire, and hence no resistance. I'm prolly burning it out.

I suppose this should be as easy as determining which wire is the idiot light and then hooking it up to pin L and just ditching the other wire all together. I'm pretty sure the only purpose of the other wire is to energize the alternator during cranking - which, honestly, what is the point?

If I want to get fancy I can hook pin S up to the + post on the back of the alternator to take advantage of the voltage sensing circuit, which if I understand correctly allows the alternator to react quicker to changing electrical load and maintaining the proper voltage.

[jmgtp]

Looks like it was the wire - I checked with a multimeter and the wire that I had connected was 12v anytime the ignition was on. The wire I did not use was 8v only when the engine was running. So, I switched the wires so the 8v wire is connected to pin L. With the motor running and that wire connected the alternator its voltage dropped to around 5v. The alternator is charging perfect and I think this should resolve the problem.