Wiring GM alternator to Toyota harness... (1 Viewer)

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Joined
Dec 3, 2007
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207
Location
Troutdale, OR
My '92 350TBI conversion into '88 FJ62 was "completed" almost exactly this time last year. I have had it wired up and running for barely a year now and have been slowly trying to "clean up" some of the circuitry. It's been a daily driver though since I first got exhaust put on it.

So I pulled into the driveway this afternoon after sweating it out for a few miles in traffic watching my voltmeter drain down to the number 8...opened the hood and checked the battery and alternator with a voltmeter and realized both were in bad shape. On top of that, I realized that my fusible link going to the alternator (heavy gauge white wires attached to stud on alternator) was also worn and looked like it had taken some heat. (It was barely attached to the battery which I am assuming is at least half my problem)

At this point I'm looking for some advice on wiring up the alternator correctly before I try to burn up another one or worse yet cause a movie-like explosion. (BTW, I have the FSM wiring diagram for the Toyota and a cr&ptastic Chilton's manual for the chevy.)

GM alternator has:

-large stud/nut on back

-pig tail with:

-red wire -12 gauge (Chilton diagram shows it going to bat. w/ fusible link)
-brown wire -14 gauge (can't tell exactly what it should go to...ignition switch?)
-black wire -14gauge (Chilton's is not very helpful for this one either)

Toyota harness has:

-two heavy gauge white wires to an eyelet (Should go to the stud on Alt I presume?)

-white wire ~12 gauge (*this wire does not show up in the wiring diagram?)
-white/yellow wire ~14 gauge (to 10 amp fuse & ignition main relay)
-black/yellow wire ~16 gauge (to 7.5 amp fuse & charge light relay)

Like I said before, I've had it running for a year now so if noone has any input I'll just keep it the way it is and see what blows up next. But if anyone were to have some advice I'd be all ears and very appreciative. Thanks in advance...

-Darin
 
Sounds like you have a 3 wire GM alternator.

I prefer the 2 wire ones, and then u just wire the regulator wire to the fuse and charge light relay(regulator), and the other to the main relay. run a cable from your battery to the large stud on the back and your done.

I did this on my BMW a long time ago, $50 for a 130 amp alternator as opposed to $350 for a 85 amp alternator...
 
GM alternator has:

-large stud/nut on back this goes to the + side of the battery with a fuse or fusible link

-pig tail with:

-red wire -12 gauge (Chilton diagram shows it going to bat. w/ fusible link) dont need the fuse just connect it to the large + lug on the back of the alternator, (this is the wire that senses voltage
-brown wire -14 gauge (can't tell exactly what it should go to...ignition switch?)this is the charge indicator light, it needs to go to a small light that you can mount any where on the dash then to a wire that is hot only when the ignition is on
-black wire -14gauge (Chilton's is not very helpful for this one either) the black wire is the feld wire and like the charge wire it needs to see a hot wire when the ignition is on, but dose not need a light

GMtoToyota.jpg
 
thanks for the replies...the schematic is more helpful than my chilton's...

looks like i should hook up the brown wire (GM pigtail) to the black/yellow wire (Toy) for the charge light relay. (which is what i currently have connected)

i'm still wondering about the toyota side...the single white wire ~10/12 gauge doesn't show up in the FSM.

right now i have the red wire (GM pigtail) hooked up to the mystery white wire (Toy), but 4runner is showing that wire hooked up to the two heavy gauge wires on the stud/nut on the back of the alternator.

if that's the case then what happens to the other single white wire (from the toyota side)?

sorry, hope this isn't too convoluted, and thanks for the help!

-darin
 
I believe your GM alternator requires a 5 volt source to the exciter coil. That is the primary reason they do not live long in Toyotas. You can run resistors to get the Toyota's 12V source down to 5V or you can build a GM alternator with a self-exciting regulator (they cost $10 to $15), run a single wire right to the battery and eliminate everything else. I have been running that setup for the last ten years. Effective and clean. You can buy them pre-built if you prefer from Summit, etc.
 
thanks for weighing in lehi...

so pardon my technical ignorance, but, what are you saying?

in my thread research i have read that toyota's don't like aftermarket alternators in general...the way i had it wired up seemed to produce voltage to the battery and allowed my voltmeter to work...i'm just wondering if there is a "correct" way to go about it.

i'll look into this "self exciting regulator" just because it sounds interesting, but are you saying that there's no way around burning up alternators without it? and is there any provision for the toyota voltmeter with that set up or are you just running an aftermarket? or none?

found this: http://www.alternatorparts.com/what_is_a_self_exciting_alternator.htm


there's only so many carquest's here in town and their warranty policy is bound to catch up with me sooner or later...but if i move in the next year...hmm.

can you tell me what this mystery white wire is? does the FJ60 have it too?

thanks again-

darin
 
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I put a Delco CS130 alternator (same alt as was on my old '91 Suburban 5.7l TBI) on my '84 Xcab a couple years ago. Haven't had any trouble with it and the charge light works fine. I don't recall exactly how I wired it, but I did use the original Ign wire to the regulator to excite the alt. and there was one wire that I simply didn't connect at all. The voltage sense wire I connected to the output stud of the alt.
Either there's something I'm missing or people aren't connecting the domestic alternators correctly. Their excite wire should come from the charge warning light in the dash. Which leaves only the voltage sense wire and the output wire/cable to connect if not an ECU controlled engine, and may even if it is ECU controlled.
 
i think i "understand" (used very loosely) that the self-exciting alternator is a one-wire alternator as opposed to two or three wire alternators.

so on my three wire alternator with 4/5 wires coming off the toyota harness (see first post) i am going to hook up:

-the red wire to the stud/nut for voltage sensing (which i currently have hooked up to the mystery white wire mostly because i'm inept at these things and it seemed logical to tie the heavier gauged wires together)
-the brown wire to toyota black/yellow (Toy) for charge light relay (which is currently the way i have it)
-and the black wire to the white/yellow (Toy) for ignition power.

and the mystery white wire will be omitted...that seems to jive with the diagram above as well...i will try this to see if it works any better.

also good info and parts potential was found here:

MadElectrical.com - Mad Enterprises

check out their tech & workshop tips page!

they also have fusible links and this little number (kind of unrelated by i saw ntsqd's set up and am looking for something similar):


onewir13.jpg
onewir13.jpg
 
TBI Chevy trucks had a very usefull five-post terminal for things needing to go directly to the battery. I bet you can yank it from a wrecking yard for a dollar.
 
The MAD part is an mid-ish 60's to mid-late 70's GM car part. Usually found on the radiator core support or the firewall. '73 to late 80's-early 90's GM trucks have a two stud version of it on their firewalls. Neither of them is really meant to carry starting current which is why I used the marine part in the 60's engine bay, but I collect the above mentioned parts when I see them as they often come in handy. I have one under the rear of both the 60 & the Xcab as well as one under the front of the bed of the Xcab carrying breakered battery power for various needs.
 
okay, so i just got it all hooked back up...wired as described in post #8...motor turns over and runs...voltmeter gauge showing <12 volts

my external voltmeter is not showing any charging happening...12 volts at the battery and rear post of alternator...

i took my 1-year old alternator for warranty-exchange last night to carquest and had the battery (1-year old also) charging for the last 24 hours...was showing 12.8 volts.

am i being stupid about something? (be gentle with your answer to that)
 
okay, so i just got it all hooked back up...wired as described in post #8...motor turns over and runs...voltmeter gauge showing <12 volts

my external voltmeter is not showing any charging happening...12 volts at the battery and rear post of alternator...

i took my 1-year old alternator for warranty-exchange last night to carquest and had the battery (1-year old also) charging for the last 24 hours...was showing 12.8 volts.

am i being stupid about something? (be gentle with your answer to that)

i personally wouldn't try to use your stock harness just wire it up how i did on post 3 i just finished wiring one it and it works grate.
 
still no volts...

i personally wouldn't try to use your stock harness just wire it up how i did on post 3 i just finished wiring one it and it works grate.

hey 4 runner, thanks for following up. i do appreciate your input. can i ask where you got the schematic above?

the two heavy gauge wires DO run directly to the battery. those are the two i have on the rear stud of the alt. i hooked the new alternator up with the red wire going to the stud as well, and the other two wires as i had them before. i am trying to keep the voltmeter on the dash working, since it was before, and i know which wire runs that. there's a half dozen threads on wiring GM alternators in conversions, but none dealing with three wire alternators and none of them offer complete write ups, especially for the FJ62.

at this point:

-i've inspected, repaired and/or replaced all the fusible links.

-the "new" alternator is not producing any current. i'm taking it to have bench tested today and possibly to replace it (again).

-i'm hoping from input from anyone else who's had experience with this...
 
(BTW, I have the FSM wiring diagram for the Toyota and a cr&ptastic Chilton's manual for the chevy.)

Just FYI, the Chilton's Landcruiser manual has the same diagrams as the Toyota FSM ;)

More constructive:

On my swap (5.3) i don't have the fusible link connected to the alternator, its just connected to a battery 12V+ source. There is a fusible link in the stock chevy harness that runs from alternator to battery. It's probably a different setup on the TBI...
 
Just rebuild the alt. get some new bearings (not Chinese) new brushes and a new self exciting regulator. The whole thing will cost less than $40 and one wire is hard to mess up. The regulator requires some soldering work, but it's easy enough to do then you're golden.
 
Just FYI, the Chilton's Landcruiser manual has the same diagrams as the Toyota FSM ;)

(The chilton's manual i have is for the vehicle that the chevy motor came out of, and it's wiring diagrams are severely lacking. The toyota FSM & Haynes are good.)

and lehiguy- i am seriously considering the one wire set up or 4-runner's set up above.

i guess the purpose of this thread is to not only solve my problem (first and foremost) but also to provide some more information and or options for wiring GM to FJ62...the other threads on the topic don't seem to get completed.

i just got back from carquest...the alternator tests "good," putting out 14+ volts on their machine. for some reason i'm not getting voltage out of it when installed on the vehicle.

the other day i began re-wiring my GM coil and ECM (trying to get them powered from the toyota fuse box). i'm wondering if this wasn't the start of my problems, so i'm going to re-trace my steps there first. :bang:



thanks again for any input!:cheers:
 
The resin I wouldn't use the stock wiring is that for one this alternator has a higher out put so upgrading the wiring is a good idea and two Toyota tents to use negative signals for there meters, switches and other major parts, where this GM alternator requires positive signals, as far as your volt meter I believe it will still work just fine, if you r worried about the meter not working just take a look at the cruisers wiring diagram and trace where those wires go and be sure there still hooked up
 
so i've put all the wiring back that i messed with the other day.
i've replaced or repaired all the fusible links.
the battery and alternator are tested and good.

i have the alternator wired back up the way i had it for the last year.
(and i also tried variations on what others have suggested)

symptoms still the same:

battery is charged, motor turns over and runs...but there is no voltage coming out of the alternator.

everything is set up exactly the same as i had it before when i was getting 14+ volts out of the same alternator.
i confirmed 12v power to the alternator with ignition on.

4runner- I have tried it set up exactly as you have shown in the diagram.
the only difference being that the wires running direct to battery are 8/10 gauge which i realize may be small for the amp difference in alternators.
i am going to get some heavier gauge wire and try but...


everything i do is a WAG at this point. i think i'm going to end up taking it to the shop on monday.
 
Is your charge light in the dash burnt out? It doesn't sound like your getting the alternator to excite.
 
i'm not sure the light has ever worked. i've always relied on the in-dash voltmeter.
it didn't go on the other day when all this began...

would the charge light interrupt the circuit?

i thought it just took 12v to the alternator, ignition on, to "excite it"

thanks
 

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