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Old 08-22-2021, 06:08 PM
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Alternator Plug Connector

Does anyone know where you can find the male connector for an alternator (normally built into the alt). I bought a higher output alternator, and the voltage sense and excite wire plug is a GM version. Instead of adding more random wires to get it to work, I want to make an adapter, but I cannot find a male plug end. I'm also making an assumption here that the two PCM wires (W/G and BR/R) are what the new alternator needs, but I'm not sure about that.

My instructions from the manufacturer were "L goes to ignition with a 470 ohm 2 wat resistor inline and S terminal goes to b+." The connector supplied for the new alt has 2 wires labeled L and S. From what I've read for OEM wiring, BR/R is the voltage control wire, and the W/G is the excite wire. So couldn't I just use the OEM wires (provided I can make an adapter)? If I do that, do I need the resistor?

If I cannot use the OEM wires for the new alternator, I'll run new wires. If the S wire needs battery positive, can't it just go to the B post on the alternator? For an excite location in the engine bay, would the Ignition fuse B/Y wire be the best candidate to splice into?

Old 08-22-2021, 06:42 PM
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looks like its just gonna need the two wires going to the same place the stock ones do at the ecu and the chrome post gets the fusebox wire. dont mistake the black nut below for B+ its referring to the post above for the fusebox wire which is on your 120a fuse from battery. i dont see why you couldnt just cut em back and save the original alternator plug for swapping back later if you want. adapter harness means more points for bad connection imo
Old 08-22-2021, 07:33 PM
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Originally Posted by RastaRx-8
i dont see why you couldnt just cut em back and save the original alternator plug for swapping back later if you want. adapter harness means more points for bad connection imo
Do you mean splice the OEM wires between the PCM and the female plug? I suppose that would be a low risk idea to try.

I think I found the male plug though for the record. The discussion is about a FD3S alt, but I'm pretty sure it's the same as the RX-8.
Found - Replacement alternator connector for S5 FC3S and FD3S

Part number C1900.
Old 08-22-2021, 08:04 PM
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ill plug in my extra harness to my fd's alternator and make sure but i am 99% sure already

there is an "alternator control" Brown/Red pin 2i and "alternator volt" White/Green pin 2t according to my pinout chart
Old 08-25-2021, 11:16 AM
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So my idea to make a harness adapter and use the PCM signal wires won't work apparently. I'm still a little confused as to why exactly, but most of that is because I'm not an alternator expert and the customer service I've gotten is pretty pathetic. That being said, I apparently will have to run new wires to battery + and a 12V ignition source, bypassing the PCM. That would mean the alternator is self regulating based on battery voltage feedback. I guess I'd consider that to be a "smarter" alternator than our factory one, since OEM is controlled by the PCM.

I guess we'll see what gremlins appear when the PCM no longer is getting alternator feedback...
Old 08-25-2021, 11:45 AM
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the pcm is way more accurate than an alternator regulator which will prob kill your battery faster. the wires wont matter because one controls the other basically ... i am not an expert either tho or i wouldnt have told you to try lol
Old 08-25-2021, 03:25 PM
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I think as long as I'm around 14V with it running, it shouldn't negatively affect the battery. Right now with the stock alt, I'm getting anywhere from 13.4 - 14 V. So as long as the new one outputs around that and doesn't exceed 15, I think I'll be good.
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