Quick Question Regarding Alternator Wiring.

[Duffman692002]

I'm in the midst of cleaing out all the unused wiring since I've got a carb'd 13B and no emissions. Car is an 85 GSL.

Well I've started rewiring the emission harness and have got the water temp and oil temp completed, now I'm somwhat stuck on the alternator. On the back of the alternator is the female connector containg the WB/BW wires, whilst I've sorted the WB wire out and got it replaced I can't figure out the BW one.


With the loom pulled off the car and tape removed I found that the BW wire becomes many:


I'm reasonably certain that the BW wire out of the female connector is the one all the other wires are leaching off off and I think that's the only one I need.

Finally the single wire splits again and this is the bit that has me stumped.


The top BW wires is what looks like the same wire from the female connector and the bottom one leaches off of it.


Now with that outta the way, my question is which one do I need to save? Top, bottom, or are both needed? I'd assume the top one is the only one I'd need but I can't make sense of it, lol. I've got the 85 FSM open in another window and I've just gotten myself even more lost.

Since I've had a hard time figuring out this lil bit I decided to make up my own lil harness and see what does what. Basically I've copied what Mazda did with the stock harness but apparently I've overlooked somethings.

This is what I mocked up for the BW wire coming off the female plug. Wire with the black zip tie is the top wire in the plug:

WB wire is ran as Mazda desinged to the pin on the smaller of the two harness plugs.

As Mazda did with theirs I jumped the single wire into two with the vampire clip problem is now is it won't kill the car through the ignition switch. With the ignition switch in the OFF position: Pull the top one apart, still runs. Pull the bottom off, still runs. Disconnect both, car dies. I know I'm missing something obvious here but I've been studying the FSM for so long that I can't make since of it.

[TitaniumTT]

Damn AJ, Thats a stumper for sure. Usually one wire color does one thing. In the FC the BW wire is an ign hot. It seems that somewhere along the line one wire was changed to a constant hot and the other left as an ignition. I think you're going to need to trace both of them back and see which one is the constant, and which is the ign hot, the ignition hot needs to go to the alt.

[3rd and final 7]

do you a FSM

[3rd and final 7]

i looked at the wiring diagram and it shows goes from the alt to connector x-07 which is the yellow plug on the other side of the engine bay just where the wwiring goes in the firewall then 1 branches to the choke and check relay which branches off 1 more time b4 it gets to the relay, one goes to a fuse which in one dicretion goes to anther fuse for the kick down switch which i belive is for a A/T, in the other direction it goes to the ignition switch. thats all it shows you can go to http://foxed.ca/foxed/index.php?page=rx7manual#firstgen and D/L the manual to your pc you going to be looking for page 50-10 or pdf pg 10

[Duffman692002]

Originally Posted by 3rd and final 7

i looked at the wiring diagram and it shows goes from the alt to connector x-07 which is the yellow plug on the other side of the engine bay just where the wwiring goes in the firewall then 1 branches to the choke and check relay which branches off 1 more time b4 it gets to the relay, one goes to a fuse which in one dicretion goes to anther fuse for the kick down switch which i belive is for a A/T, in the other direction it goes to the ignition switch. thats all it shows you can go to http://foxed.ca/foxed/index.php?page=rx7manual#firstgen and D/L the manual to your pc you going to be looking for page 50-10 or pdf pg 10

Thanks 3rd and final 7, that's actually the FSM I've been using. According to the FSM the -> symbol is the one for DIODE and if it's the choke/check relay that's causing me to have this issue, I could just put a diode inline with the WB wire and that would keep it from runnin with the ignition in the OFF position no? This is the first time I've done any major electrical work so if I come off as a bit dull, that's why.

[TitaniumTT]

Lies! You're so good at electrical you've created the only non-ECU Drive By Wire FB that I know of

Aight, now that I've seen the wiring diagram I think I got it figured AJ. That check and choke relay has a diode on the coil. Without that relay/diode the car would remain running. So yes, I believe if you put a diode in (I would get the biggest you could) the power shouldn't be allowed to backfeed and keep everything running. Worth a shot.

[Duffman692002]

Originally Posted by TitaniumTT

Lies! You're so good at electrical you've created the only non-ECU Drive By Wire FB that I know of

Aight, now that I've seen the wiring diagram I think I got it figured AJ. That check and choke relay has a diode on the coil. Without that relay/diode the car would remain running. So yes, I believe if you put a diode in (I would get the biggest you could) the power shouldn't be allowed to backfeed and keep everything running. Worth a shot.

Well I guess I'm actually a genius, too smart to see what I've fuged up on my wiring though.

Clean, then that's what I'll do. Thanks guys, you've been much more helpfull than the other forum was. Should have come here first.

Actually, I still haven't figured out why it splits into two or if i even need both now that I'm going to pu that diode in. Looking at the FSM, one of the wires comes outta tha relay but since it's gettin' eliminated there is no need for both correct? It would just be a matter of finding out which of the two BW in the plug run the car. As I said earlier, I'm fairly certain that it's the top BW wire so I'll start there. If it works then I'm done.... I hope.

[rx4ur7]

It is staying running because the alternator is still energized. You should just be able to hook up the Check and Choke Relay.

That B/W supplies power to alt/CCR; auto trans; coils; F/P: nearly every circuit in the vehicle.
Check out the W-1 page of the wiring diagram. It shows where all the main wires go and shows where to look if you are having odd problems. Many circuits can be affected by something wrong in a different circuit. Very rare I remember 4 I have seen, two human caused, one corrosion in wiring harness and one packrat.

[Rogue_Wulff]

The choke and check relay also turns on/off the dash warning lights. Anytime the key is on, but the alt not charging, the dash warning lights all illuminate. This can happen with the key on/engine off, or engine running/bad alt.

[TitaniumTT]

AJ, I would leave the double/spare wire in the harness. Just terminate it inside the harness or even better yet, throw a single pin Weather-Pack terminal on it. This way, if you ever need a low amp ign hot power source to energize a relay, it's already there.

IE: If you ever decide to drop in an electric fan, or fog lights, or anything like that, you have something that can energize a relay when the ign is on and then shut off with the key off.

[12arotary]

wait, is it a 12a or a 13b im just curious

[j9fd3s]

this thread saved me tons of headache on mine! i'm basically started from scratch, and alternator works

[Duffman692002]

Originally Posted by 12arotary

wait, is it a 12a or a 13b im just curious

Originally 12A, swapped to 13B, and now has a BP'd 12A being built to go in.

Originally Posted by j9fd3s

this thread saved me tons of headache on mine! i'm basically started from scratch, and alternator works

Haha, glad it helped you too. I actually haven't had a chance to go and implement what I've learned here yet, other things have come up since and the harness took a backseat to them.

I'd like to see what you did though, wanna post up a pic?