Hey everyone. I've searched and searched and found some answers on this, but can't seem to get it right. Maybe cause I'm not too fond of electrical work.

So, I just installed a FD alternator in my 83 GSL. To my understanding I need to have the B terminal to battery + (my B terminal goes to fuse block, then connected to starter, then to battery all 4 guage wire). S terminal on alt goes straight to battery + (constant). The L terminal goes to the original white/black dash wire from the alt.



I saw a post in ausrotary saying that diodes and a relay is needed in the wiring to get this working properly?



The original white/red B terminal wire taped off and forgotten.

So, which is right?

Who here has done the FD alternator into their FB? I'm reading 13.30 volts at the battery and alternator when the car is off. When I start the car in this configuration I'm getting 12.37 volts at the alternator.

Looking for those of you that have FD alternators in their FB to help out. Thanks.

 

I did my friends car a few months ago.he has battery in a the rear of car,
Car also already had a fc fuse block mounted in the engine bay.ran two 8 gauge wires from the fuse block to alternator B+ and S terminal and L terminal to W/B wire
No issues in the 2-3 months it's been installed.
I used the same diagram as you posted on top

 

Thanks for the reply. Mine is wired up nearly the same. 4 guage alt B terminal to fuse block. S terminal going through a 14 guage wire itself straight to the battery + for constant reading. L connected to W/B. I'm not sure why my alt isn't charging. It's supposed to be a brand new FD alt.

I'll go get the alt tested I guess, but does it sound like I'm missing anything?

 

I've confirmed I've got the wiring right. B terminal to battery +. S terminal to battery (constant 12v+). L terminal to white/black original L terminal wire. I checked the L terminal to see if it has continuity and it does.

When the car is running though, the L terminal has 0 volts running though it. I've heard it's supposed to have 1-3 volts.

I'm going to get the alternator tested tomorrow. Now I'm kinda hoping my brand new alternator is bad...

If not I'm going back to a properly wired up S4 alternator 😔

 

So the FD alternator tested out good.

I'm lost on why it won't charge my car though.

B terminal goes to fuse block. Does this need to go straight to battery instead and be fused itself or can it go to fuse block like I have it?

S terminal to constant 12v+ source.

L to L terminal (white/black wire)

I have it wired in like all the diagrams here suggest.

Only thing on L terminal I was thinking is that wire goes to choke and check the relay too. If I took out my actual choke and the connector for it years back would that circuit be incomplete? If I reinstalled a choke and connected that connector would that help?

Anyone got some help on this?

 

It couldn't hurt to run B through a fuse off the battery. I plan on running mine through the 2nd gen fuse block on the tower.

You might be on to something with the choke part. You may not need to install the relay, but just ensure the circuit is complete.

 

My bet is that your L terminal wire isnt supplying 12V switched.

I had one that wouldnt power up before. Caused the choke to never *stick* when you pulled it. I ran my electric choke set up on several carbs through that wire with no issues as a 12v switched source. I have an electric fan hooked up to it right now with no issues, too.

 

I had a friend saying that I have the B terminal cable wrong. Said that from the B terminal the cable should either go to the fuse block, then straight to the battery or go from the alt B terminal straight to battery(fused).

I have it going from the B terminal to the fuse block, down to the starter +. The positive battery cable also connects at the starter +.

I'm reading the same exact volts at the alt B terminal as I am at the battery post when the cars off. Why would ditching the starter make a difference?

I don't think the choke and check relay is in the car either 😔. I wonder if that's my problem with the L terminal. I'll look into getting the relay and choke back in the car.

Wait the L terminal white/black wire is supposed to be 12v+ switched???

Hmmm I thought the L terminal was to "excite" the alternator to let it know to start charging?

That could be it, but I thought the L terminal wasn't supposed to be 12v+ switched. I heard it's supposed to only run 1-3 volts through it.

I'm still lost here.

 

You were right! Wow that was simple. I connected a switched 12v+ source to the L terminal and 14.5 volts right off the bat when the car was cold.

I will do some test driving to make sure all is fine tomorrow.

I didn't know the L terminal was supposed to get 12v+ switched.

Thank you!

 

That's incredibly odd. Both my 84 and my 83 have FD alts and they're wired up as per your original setup, working fine. In fact I just installed the FD alt in the 83 earlier this afternoon and drove it for nearly an hour showing 14v on the cluster voltage meter.

B terminal hooks to the original harness white-red wire that goes to the main fusible then to the battery (had to put on a larger ring connector). S terminal on the 83 just loops back around and hooks to B terminal with another ring connector, while on my 84 I gave it its own fuse on my 2nd gen fuse block, either way it sees constant +12v. L terminal hooks to the original "dash" wire on the car's harness that goes to the choke/check relay and the dash light.

You might want to check to see if your choke/check relay is working properly. I blew two alts when something inside my choke/check relay messed up. That was an expensive little troubleshooting process, FD alts aren't cheap to rebuild! You might have a similar but opposite problem where yours is stuck open and never gives voltage where mine got stuck closed and kept shorting out.

Jon

 

His original black/white wire has no power now, since he removed the electronic choke assy. I went through the same problem when I removed mine a year ago. Somewhere along the lines, power comes from the ignition switch, THROUGH the relay/electromagnet, then makes its way out to the engine bay. If you remove any of those parts, its just a dead wire.

The original pin for that supplied the power for that wire is somewhere under his dash now, doing nothing haha.

ALSO: I know that wire IS 12v switched on the FB at least. Like I said, I found out it was while installing other aftermarket things that needed 12v switched. After a couple minutes of testing wires with a voltmeter, I found that one to be pretty accessible. I have one right now wired to an efan for 12v switched and it works like a top. Used the same wire for electronic chokes on aftermarket carbs, lighting kits, etc.

 

heres like a universal 3 wire picture:



I know its not a Mazda alt, but you get the idea.

You have your 1 pin reading the battery, 1 heavy wire that sends the charged power to the batt, and one that supplies power to the regulator to make it work.

His wasnt turning on, which is why it wasnt charging.

The choke and check is a super simple thing that basically ensures your dash works when it "senses" the alt working. I have personally driven 2 blocks in a GSLSE without realizing the alt was unplugged because it didnt throw all of the idiot lights at me to let me know the alt wasnt turning.

If his dash works while that wire is unplugged, cool beans. It could have also been modified at some point to get its power from somewhere else. (like that SE, i think)


IGNORE THE LABELS ON THIS DIAGRAM. its NOT a mazda alt. The wiring does not coincide with any mazda diagram, lol. Its just to show how a basic 3 wire alternator works.

 

Thanks for all the help guys! I've been meaning to get on and see if there was more info, but i've been busy with other things and the car has been resting lol.

I do still have a charging issue it seems. I have my sense wire 12v + constant, dash wire hooked up to a ignition switched 12v + source and the b terminal to battery of course still.

I noticed that when I have the trickle charger off my car that my battery will die after just a few days to a week of sitting. Something in my car is still bleeding off the battery while the car is off or it's all wired wrong. I leave the car on the trickle charger most the time cause I only drive the car once or twice a week maybe.

I also have been having idling issues and my tuner thought it was originally my S4 NA alternator. We were showing low volts at idle at around 11.7 while running... yeah, that's no good!

I upgraded to the FD alt and now see 14.3 volts while the car is running. After warming the car up and driving it and sometimes coming back down to idle the car will start to stutter sometimes and act like it's going to die at idle. It won't die, but I noticed when I caught a hiccup with the voltmeter that volts went from 14.3 volts down to 13.5 and back up to 14.3 volts. I don't know if that was a electrical issue or from it almost dying out cause the electrical charge just isn't there at such low rpm when the car is stuttering.

Car drives fine, cruises fine, and pulls like a beast especially in boost! Just can't seem to have a steady idle and my battery dies after a week if not on trickle charger. Only thing wrong with my car

 

something is def awry there...

I would explore the harness looking for something that could be draining. Do you have an MSD by chance? Sometimes people wire those wrong and they are turned on as long as they are hooked to a battery...

 

anyone have a pic for wiring an FD alt onto an SA with the 4port plug ?

 

twinkletoes,
I have the same issues as you and basically copied your last post, added changes that apply to my car's situation and pasted it below. I hope that we can help eachother solve this issue, or maybe someone else will help us. Unlike you my alternator does not currently charge correctly at idol, once it does I will be at the same step in troubleshooting as you currently are. I don't want to hijack your thread, feel free to tell me if I need to post this somewhere else.

I have S terminal going to 12v + constant,The B terminal to battery with fuze, L terminal hooked to the White/blue wire twinkletoes; you called this wire white/black on your car...(I have not traced this wire to its starting point yet). Unlike you my alternator does not currently charge correctly at idol. Do I need to do away with the white/blue wire and rewire my L to new a switched 12v ????

I noticed that when I have the trickle charger off my car that my battery will die after just a few days to a week of sitting also. Something in my car is still bleeding off the battery while the car is off or mine is wired wrong also. I leave the car on the trickle charger most the time cause I only drive the car once a week maybe.

I also have been having idling issues and my tuner thought it was originally my S4 NA alternator. I too was getting low voltage so..

I upgraded to the FD alt. At startup a or sometimes after warming the car up and driving it and coming back down to idle the car will start to stutter and act like it's going to die at idle. Unlike twinkletoes, my car will sometimes idol up and down in RPM and shutter so much it will shut off. I have had my Throttle positioning sensor checked by the tuner. That is something you may want to check on your car if you haven't already twinkletoes.

Car drives fine, cruises fine, and pulls smooth and hard under full boost without misfire. Just can't seem to have a steady idle and my battery dies after a week if not on a trickle charger.

 

here you go sh00bs... does this help? it explains some of the wire colors for different years. This is something I found on the internet, I have not checked all the info, but it has the correct colors for my car.

 

 

Sorry I'm just now seeing this. I haven't been on too much. I got my idle fixed and it ended up being the throttle position sensor for me. I recalibrated it on my standalone and solved the idle issue. I still believe I will have a dead battery if I unplug my battery tender so I just leave it connected.

Yes, same wiring as me except the white/blue wire. I have the L terminal wired up to a switched 12v+ source.

 

would a diode be needed, as seen in the below thread? i need to make sure that i wire in an FD alternator correctly.

https://www.rx7club.com/1st-generati...stion-1011841/

as a question...the wire to the dash, that's really just to any switched power source, right?