Three plug alternator harness and two plug alternator

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Pinion

Pinion

Joined
Jun 16, 2003
Threads
127
Messages
1,124
Location
Hull, Mass
Ok. WTF. :mad:

The title says it all. I get most of the cruiser together and realized that the alternator from my 79 FJ40 is a two pronger plus the battery output. The harness has a three pronger and no loop for the alternator.

I went ahead and upgraded all the positive cables to 2 ga (The one for the starter, and the one from the alt to the battery) and all of the larger ground cables are all 4 ga. I hooked the 2Ga from the alternator straight to the battery, and then the white/blue wire that feeds the fuse panel to the black pigtail embedded in the positive cable mount.

Ok, so now I cant get a spark from the coil, and that is another problem in and of itself.

Now, can someone help me with which wires I need to use from the three pronged harness to the two pronged plug?

Yeah, I know Im rambling.. :cheers:
 
the extra one is a ground.........I think
 
Thanks, but what do the two plugs on the alternator go to, and which of the three wires do I use? I cant tell which is which on the alternator..
 
TTT.

Gotta fix this today! This cruiser hasnt started for 25 years and want today to be its new "birthday" :)
 
Thanks guys, but my alternator has an "L" molded in the case for one plug and "IG" for the other. The "B" I already have hooked up.

I have a white/green, a white/blue, and a thicker gauge white/black. So, can anyone tell me which goes where?

Johnny, I have had that schem. printed out for a few weeks now. It has helped to a point.
 
The L is load, usually to some kind of excite lead. It can be as simple as a light. The IG goes to the ignition circuit. I do not know the color code for that year and it is different than my '73.

Make sure the lead you hook to the IG connector is switched or you will have to pull the coil wire to kill the engine. Don't ask how I know this.

I would imagine the large wire used to go the the amp gauge though I am just sumizing.
 
It sounds like an internal regulator alternator. If so, you won't need the original wires from the regulator except for the idiot light (if you have one). L is for the idiot light and Ig goes to the Black/yellow stripe ignition circuit that also feeds the coil, voltage regulator, etc. Try running a wire from the ignition circuit to the Ig terminal and see if it produces more than 12V.
If you are running a wire directly to the battery, it should be fused or it might cause a big smoking mess if a diode fails.
 
Thanks man! Looks like I have a fair amount of work to do tomorrow.

I think I went and totally fxxxed up my wiring just now. I think I put the wrong wires into the two ports and I think I blew the fusible link. Is it the pink wire hooked up inline with the heavy gauge black with yellow wire? Im asking because I havent seen one before, but I have an old harness I just ripped apart and saw that the BY wire was connected with about 5' of that pink wire.

Is there an easy way for me to bypass this damn thing and use a fuse instead? That damn wire runs the whole length of the dash and is entombed well inside the bowels of the wiring harness. Theres no way in hell Im going to rip all of it out to replace it.

My ignition switch was on the fritz, and I thought that was what the problem was, but I checked it with my voltmeter and it is working correctly.

Also, anyone know which wires go into the ammeter in the gauge cluster?

This has turned into one hell of a can of worms. I got it to turn over and sputter today and ended with this.
 
Pin_Head said:
If you are running a wire directly to the battery, it should be fused or it might cause a big smoking mess if a diode fails.
Click to expand...

what fuse (fuse-able link) rating do you recommend ?
I am almost done with a 12si Chevy alternator install, currently connected directly to the BAT.

thanks,
manny 72fj40
 
Pinion said:
Thanks man! I think I put the wrong wires into the two ports and I think I blew the fusible link. Is it the pink wire hooked up inline with the heavy gauge black with yellow wire? .
Click to expand...

Pink wire? Its not stock, but if it is hooked to the black wire with yellow stripe, then it is part of the ignition circuit. This is not fused, so if you accidentally ground it the wire can burn.

Pinion said:
Is there an easy way for me to bypass this damn thing and use a fuse instead? That damn wire runs the whole length of the dash and is entombed well inside the bowels of the wiring harness. Theres no way in hell Im going to rip all of it out to replace it.

.
Click to expand...

Bypass what? An internal regulator alternator needs 12V from the ignition switch.

Pinion said:
My ignition switch was on the fritz, and I thought that was what the problem was, but I checked it with my voltmeter and it is working correctly.

Also, anyone know which wires go into the ammeter in the gauge cluster?

.
Click to expand...

Voltage at the switch doesn't necessarily mean the switch is good. It has to be able to flow hte necessary amps too. The contacts could be oxidized and you could still have 12 V after the switch.

For the amp meter, it depends on the year. On early to '78, they are a large white wire and a white wire with blue stripe. Later years are small wires and I forget what the color is.
 
mr_manny said:
what fuse (fuse-able link) rating do you recommend ?
I am almost done with a 12si Chevy alternator install, currently connected directly to the BAT.

thanks,
manny 72fj40
Click to expand...

It should be a little higher than the max amp output of the alternator. I would guess about 120 A for the 12si.
 
Pinion said:
Thanks guys, but my alternator has an "L" molded in the case for one plug and "IG" for the other. The "B" I already have hooked up.

I have a white/green, a white/blue, and a thicker gauge white/black. So, can anyone tell me which goes where?

Johnny, I have had that schem. printed out for a few weeks now. It has helped to a point.
Click to expand...

The white green should be going to your voltage regulator on the passenger fender from the alternator

The white blue should run to your instrument cluster gauge since it has an ammeter (should hook up with the negative post)

The white black is a ground
 
Last edited:
I am using an internally regulated alternator.

The Pink wire which I am referring to is inside the wiring harness and can be found spliced to the heavy gauge B/Y wire the long way down the harness. I cut open this wire from my old harness and it had a plastic insulator and then 3 or 4 silver wires in it. This wire goes no where else than along side the B/Y wire.

I was thinking of bypassing the pink wire and then adding in a fuse.
 
The int reg alternator has three connections: the B+ post, the IG lug and the L lug. The L lug is the idiot light and originally had a yellow/white stripe wire that connects via a diode idiot light relay. The IG lug has a yellow wire connected to the black/yellow ignition key on circuit that is the same as the other engine accessories, like the fuel cut off solenoid. No need to run the idiot light circuit if you don't have one.

If the pink wire doesn't connect to anything then it is just junk and you can toss it. Just connect the IG lug to the fuel cut off solenoid circuit. No need to add a fuse as it should already have it.

BTW, what year do you have. This info is for 81s that have the internal regulator alternator. the color codes are the same for most earlier FJ40s.
 
I have a 72 FJ40, but I am running an all ~78-79ish wiring harness and a 2F. The wire choices I had that went to the alternator were a heavy gauge W/B (Ground Im guessing) and a lighter gauge W/G and another light gauge W/B. I dont have a pink wire or yellow one. The only colors like that that are near there are the ones that go the trigger on the distributor. Oh, I'm not using an Aisin carb (I dont have the linkages, although I have a carb I rebuilt from one of my old 60's), the engine came with a Holley carb and that is what I have now, so it doesnt have a cut off solenoid AFAIK.

I tried to jump the starter with an underhood remote starter and it still wont turn over. I am hoping that the ignition switch finally crapped out.

I bought a '79 from someone and they had rigged up some way to start it where the remote underhood starter was connected to the starter and you had to turn the ignition key forward, then pull the trigger to get it to run. It was booty-full :rolleyes: .

So I bought another harness and connected things the way they should be. Two days ago, I got everything hooked up and the battery jumped from my TJ. When I turned the key, the starter would bump before I got it past the ACC part of the switch. I found out that it seems to be a not uncommon thing and that I am thinking of picking a new one up.

I go back to work in a week and a half and I still have a crapload of body work to do. I was hoping I'd have this started by yesterday. I finally got a spark yesterday and it kind of sputtered. Im so close but this has really thrown a wrench into the works.
 
The electrons from the TJ were not compatible with the FJ, In VW circles this is reffered to by some as major warpfield collapse. Hey? Where ya going to work????

I wanna ride in your 40 when you get it to spark stumble and roar. Can't help you with your current (hahahaha) alternator problem but will track you down when I try to resurrect the LUCAS-ly challenged rover....

Greetings, Rob M Concord, MA
 
You must log in or register to reply here.

Share this page

IH8MUD Forum | Toyota, Lexus & Off-Road Community
Community platform by XenForo® © 2010-2026 XenForo Ltd.

© 2000-2026 Tie Rod Media LLC

Back
Top Bottom