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Altenator wiring issue

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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Hi, im having an issue with my alternator charging since i installed a Haltech IC-7 dash into my RB30 powered VL Commodore, i have also upgraded to a ls1 alternator which uses the same 2 wire plug as the RB30 altenator. I have a 12v feed running through a 470 ohm resistor and then straight to the altenator exciter wire, and the other altenator wire also has a 12v feed so all of the wiring is correct and double checked, the altenator is also definitely earthed to the block. When the resistor is installed the altenator won't charge.... So i have wired a 12v tail light bulb in the system instead of the resistor, this gets the altenator charging to 14.4v but the bulb will not go out it just stays on.

Any help would be greatly appreciated as it's getting pretty frustrating and it's the only thing holding the car back from hitting the dyno. Thanks

Can you post the exact alternator you have, and the exact wiring?

470 Ohms seems rather high, have you tried 47, with a 5W rating?

I think your 470 ohm resistor is too large. That allows only 25 mA of current to the excitor. I think you need to use something like 5-10 ohms (or an actual incandacent lamp). Normally once the alternator is running, it basically provides 12V, and there is no current running through the resistor (or lamp, that's why it turns off).

That may only be true using the Lamp input to the alternator. It sounds like you're going to be wasting some heat with a fixed resistor.

There are a few different "LS1 alternators". Some use field excitation, which may be able to use a direct 12V switched input, or may need some sort of resistance, some use a PWM signal. Knowing exactly which alternator you have can help direct you to a solution.

I am using a OEX brand MXA306 https://franklinperformance.nz/products/oex-140a-ls1-alternator-mxa306

I have constant 12v power running to the sense wire and a switched 12v running through the resistor to The light wire circuit.

Like i said on my post i have tried a lamp in the circuit instead of the resistor and yes that works and the altenator charges but the bulb will not go out when charging, it stays on.

I have tryed a Mitsubishi branded altenator of the same specs today and nothing has changed, still the same result.

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