2jzfc

Ok, so I'm trying to pin point the 2 prong connector for the alternator on my 86 NA. I've pulled my engine harness from the car and removed the ECU FYI. I've been looking at the wiring diagram in the FSM but I cannot figure out where it's at. In the engine harness on the passenger side, or the headlight harness on the driver side? I've found a connector in both harnesses that would fit. But neither of them have the same wiring colors as what the FSM says it's supposed to be. I'm thinking the alt wiring is in the engine harness itself, but the FSM says the two wires in the connect are black/white and I'm assuming white/black or white/blue for the lower prong.

The wires in the engine harness side are black/white and brown/yellow, while the driver side harness is black/white and from what I can tell green/brown maybe green/orange. My gut tells me it's the wire in the engine harness passenger side. What do you all think??



I highlighted the wiring in question:


It's for a turbo model, but doubt it's different:

satch

iTrader: (1)

You are referring to page 16 of the wiring document while you need to be looking at page 15 for there is a difference to begin with. The White/Black wire on an NA is found in the emission harness and not the engine harness which is for the turbo model. Both models have the Black/White wire found in the engine harness. Now the W/B wire runs to the alternator warning relay so if you find a wire in the engine bay that is also W/B you could conduct a continuity test to verify if you have the proper wire or not. Now with respect to the B/W wire this wire has 12 volts w/key to on and is powered by the engine fuse (interior fuse box). If a wire in the bay is B/W and it has 12 volts w/key to on and it loses power once you pull the fuse AND the wire rings out when doing a continuity test w/the B/W wire at this fuse then you know you have the proper wire. The B/W wire at the alternator and the B/W wire at the main relay's 2 wire plug is the very same wire thus you could use that wire to test for continuity w/the wire you think is the B/W wire in the engine bay (remember, continuity tests are done w/no key).

misterstyx69

iTrader: (142)

That connector goes to the back of the Alt on an N/A.

2jzfc

Yeah, I know it does. But I'm trying to trace it FROM the alternator to whichever harness it goes into, which I'm sure I've found already. Thanks!

2jzfc

If I don't have an ECU in the car, do I even need the two prong connector installed in the back of the alternator??

jjwalker

YES!

The S wire senses battery voltage and tells the regulator what it needs to be doing and the L wire is what energizes the field coils and runs through the charge light on the dash.

You have to have them!

satch

iTrader: (1)

And neither of these wires are associated w/the ECU. The W/B wire is associated w/the CPU.

jjwalker

Satch is correct. There are a few ways to approach this make the alternator work as intended. I'll list it from easiest to hardest.

1) Leave it alone, assuming your CPU works properly, and leave it stock. The CPU doesn't care what ECU or carb you are running.

Pros: It works with no work
Cons: if your wiring sucks or if your cpu sucks, it doesnt work.

2)Connect the S wire directly to the battery or preferably at the fuse box, behind the main relay. You then connect the L wire to the ignition relay at the firewall so that the field coil can energize.

Pros: works...it just does.
Cons: you lose the charge light. you can't rely on the volt gauge because it sucks. Carry a multimeter in your car.

If you do it this way you WILL lose the charge indicator and if the alt fails your going to be in the dark about it...this just makes it work.

3) You can bypass the CPU and run it S5 style. You can rerun the L wire directly to the charge light, so you still have a charge light. You can run the S wire the way it is or run it to the battery.

Pros: It works the best if option one doesn't work. Your charge light still works so if the alternator decides to die you have an indicator.

Cons: This option actually causes more work, but at least you keep the alternator functioning correctly with the charge light.

2jzfc

Thanks for the info guys!

OK first off, what is the CPU I'm in IT so I'm sure CPU means something different to me than what it does in RX7 lingo...

My wiring is all stock and never been modified minus me pulling the engine harness and the ECU. Pretty sure I was able to trace the 2 wire prong for the back of the alt in the engine harness I removed to a plug that I'm assuming is in the dash harness? I'm guessing I can separate the wiring from the engine harness and run it back into the cab to the dash harness plug on the passenger side kick panel, and it should work like factory?

jjwalker

The CPU is what we'd call in my industry the "Body Control Module". Mazda calls it a CPU because they where basically the first to have a computer control non-engine essential functions. GM did the same thing but named it a BCM, Ford did the same thing and named it a SJB.

The CPU basically controls all functions unrelated to the ECU. It is crude and ancient. Our RX7's have a "BCM" but my wifes 2010 mazda 3 does not. It was a technological step in the auto industry, but it was a bit early, way to early.

2jzfc

Understood!