Quick tech question re: 3 wire alternators

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HollywoodJackson
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Quick tech question re: 3 wire alternators

Postby HollywoodJackson » Thu Aug 11, 2022 1:47 pm

Greetings Nissan Infiniti fans!

Is there a way that I can determine which of the three wires coming out of the alternator are, using a multimeter? I have a swap, and an aftermarket ecu. I would like to determine what each wire is before firing up the engine for the first time and possibly sending a signal/voltage to the wrong lead.

Any info is appreciated.


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VStar650CL
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Re: Quick tech question re: 3 wire alternators

Postby VStar650CL » Thu Aug 11, 2022 3:14 pm

The short answer is, probably not. With two wires on the control connector you know one is the field supply and one is the lamp driver, and you can give the unit power and ground and see which of the two wires goes to ground (that will be the lamp driver). Three wires means one of them is a PWM or analog output control ("smart" alternator), and that may show an ohm reading just like the field supply if the alternator isn't operating. If the terminals aren't marked and you can't identify the donor vehicle, you may need to disassemble it or just take your chances.

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NukeKS14
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Re: Quick tech question re: 3 wire alternators

Postby NukeKS14 » Sat Aug 13, 2022 9:46 am

You'd have a lot more success searching Google for a wiring diagram or pinout for the model of alternator you're using.

HollywoodJackson
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Re: Quick tech question re: 3 wire alternators

Postby HollywoodJackson » Sat Aug 13, 2022 10:30 am

NukeKS14 wrote:
Sat Aug 13, 2022 9:46 am
You'd have a lot more success searching Google for a wiring diagram or pinout for the model of alternator you're using.
For sure! I pulled the alternator from a 2001-2005 Toyota Tacoma I believe. I'll look again for wiring information.

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VStar650CL
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Re: Quick tech question re: 3 wire alternators

Postby VStar650CL » Sat Aug 13, 2022 1:32 pm

If it's off a Tacoma from those years then it isn't "smart", the third wire is ignition power for the regulator. That's the middle pin on the connector, so you should be able to sort out the other two by putting 12V to the middle pin and grounding the alternator body, then putting a test lamp from 12V to each of the other two pins. One should light the lamp brightly, the other dimly or not at all. The bright one will be for the charge lamp. The dim one will be for the field coil and should go to the battery (fused) when installed.

HollywoodJackson
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Re: Quick tech question re: 3 wire alternators

Postby HollywoodJackson » Sat Aug 13, 2022 1:42 pm

VStar650CL wrote:
Sat Aug 13, 2022 1:32 pm
If it's off a Tacoma from those years then it isn't "smart", the third wire is ignition power for the regulator. That's the middle pin on the connector, so you should be able to sort out the other two by putting 12V to the middle pin and grounding the alternator body, then putting a test lamp from 12V to each of the other two pins. One should light the lamp brightly, the other dimly or not at all. The bright one will be for the charge lamp. The dim one will be for the field coil and should go to the battery (fused) when installed.
Thanks for the solid info!

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VStar650CL
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Re: Quick tech question re: 3 wire alternators

Postby VStar650CL » Sat Aug 13, 2022 1:58 pm

:dblthumb:


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