A common modification on early Toyota Pickup's and 4Runner's is to replace the small factory alternator with a GM 2-terminal 10si or 12si case alternator. You can pick up a 100A or 140A Powermaster from http://www.summitracing.com (Manufacturer's Part Number: 47294, Summit Racing Part Number: PWM-47294). You can purchase the alternator bracket from http://www.trail-gear.com. Many people doing this swap replace the factory 5-wire Toyota alternator (Sense, Ignition, Alt Light, Ground, Output) with a 1-wire alternator for simplicity's sake - although all 10si and 12si alternators come 3-wire capable. The only real advantage to a self-exciting (one-wire) alternator is that it is very easy to wire - obviously. However, in my humble opinion it has many drawbacks including:

- Inability to do remote voltage sensing likely to result in low system voltage and poor electrical performance.
- Related to its inability to do remote voltage sensing a powerful self-exciting alternator can cause damage overcharging when re-charging a battery with a low state of charge.
- When used in low RPM range it may not generating sufficient alternator RPM to get the alternator to self-excite.

All it takes is a little research and a few minutes of extra time to wire it up properly as 3-wire.

1) Once you have your new high output alternator installed you need to pick up an alternator wiring harness. I got mine from Partsource it says HP3870 GM 1963-1990.


2) Match the pins on your new alternator to the corresponding plug on the wiring harness you just picked up. Don't connect it just yet but make a mental note what wire goes to what pin. It only plugs in one way.


3) Cut the plug off your Toyota harness.


4) Connect the wires coming off the alternator wiring harness with the corresponding wires on your Toyota harness.
#1 goes to the Toyota yellow "L" (light) wire.
#2 goes to the Toyota white "S" (sense) wire.
The Toyota red "IG" (ignition) wire is left unused.
Connect the + post on the new alternator to the + post on your battery using 4ga high quality cable.
Tape up and secure any unused factory wires.
NOTE: you should also connect a 50 Ohm resistor in parallel with the #1 light wire so that if the bulb burns out the alternator will still be excited.


That's it, your done. Connect the alternator wiring harness to the terminals on your new alternator. Enjoy being able to run your winch or your rock lights without worrying about your truck stalling.

 

I do not think the Toyota Factory Charge light circuit works with this wiring method- Yes or No?

 

I don't see why not.

 

Attached you will find a PDF for ’85 Toyota 4Runner Alternator Upgrade Project by Al Dolney. It's an excellent resource.

Here are some more helpful links I've compiled:

Link to 140 amp Powermaster 12si case style alternator from Summit: http://www.summitracing.com/parts/pwm-47294

The Alternator BibleBy Bill "BillaVista" Ansell (excellent info in here on alts and for wiring your alt):
http://www.pirate4x4.com/tech/billavista/Wiring/Part2/

Thread with good info on other people who have done this swap before:
http://www.pirate4x4.com/forum/toyot...-get-them.html

Some part numbers for the PWM 47294 alt. swap:
-new NAPA belt number is 7360
-GM pig tail number is 85841
-Bussman fuse holder is 782-1143
-175 amp fuse is omeg175xp from local napa
---------
update part numbers (from NAPA):
Fuse holder: Balkamp 782-1143
Fuses for this holder: Balkamp 82-1138 (150A) Balkamp 82-1136 (100A)
They have fuses in this style up to 300A at Napa

 

Good job I did the same thing post #93

https://www.yotatech.com/forums/f199...12/index4.html

 

i wired my gm 12si just like this and i have a constant .5 amp draw from the battery which kills it just sitting overnight. ive tried a bunch of diff diagrams ive found off the net, and neither work. any advice? if i pull the plug out the back of the alt(term 1+2) it drops to 0.0 draw on the battery. if i pull the 7.5 amp fuse under the hood the draw goes away as well. what am i doing wrong?

and ive seen other diagrams that say the number 2 on the alt goes to the pos post on alt, i do that and it throws a charge light on the dash and the alt doesnt charge the battery.

 

That 7.5amp is a typo?

 

right on good job!

 

the charge fuse 7.5 amp in the box near the battery.

i split apart the wire loom from alt wiring to fuse box and found one section of wire where the two thicker guage white wires connect, was corroded into white powder , its weird, ive had an optima in there for almost 5 years so no battery leakage lately. fixed that and checked all the wires. will report back tomrrow when i work on it more, going in for the night.

 

update-
so i cleaned up a bunch of wiring, cleaned grounds even more thorough.
i have it wired up with the gm alt harness white wire to yellow toyalt wire, and red looped to the b post on alt. 12.7 v battery with key off, and 14.5 with it running instantly, but it still has the charge and brake lite lit up .i redline it, thinking maybe if it hits a certain rpm itll go away but no luck. ill look into getting that resistor, maybe it will help with the light? no parasitic draw as of today as well so im happy about that.

i also have noticed i have a hard time finding key on hot wires. the ones the 85 fsm and my 86 fsm wiring diagram have labeled as ignition key on hot wires are constant hot, might have something to do with it.

the truck sat outside at my previous rental houses with no windshield, rear window or doors for about three years, so i know the rain and dust have done some damage, but not sure of the extent.

fck it i just want it running for some summer night runs and the next fall/winter wheeling season. next spring i plan on ditching my body and exo and going for a ftoy chasis, then it will be stupid easy wiring needed to run the damn thing.

hope it works out.

 

So the terminal on the back of the alt is not used? Just the plug?

 

.....

 

I don't know what wires I hook my 2 GM alternator wireless too. In the pic it shows Toyota having yellow,white,and red wires to alternator,while my plug in on my Toyota has yellow,green and black wires. I don't know what to wires to use. Please give me support on this. Thanks Mark R.

 

i recall sweating the stress of adding the resistor when i did my powermaster 47294 conversion back in 2015 or so, and i never actually did it... according to the directions it's not necessary, but as you indicated some degree of skepticism is warranted, regarding what rpm actually excites the charge function, so here are those details.

beyond that, 1-wire gm alternators were put on millions of gm vehicles, so i'm not going to worry that their voltage-sensing capability is somehow inferior to the multi-connector hookups that toyota and others used... if you have a need for 100-150 amp alternators it would be a good idea to wire up an in-cab voltmeter across the battery terminals and measure the charge function for yourself, when using high current situations like welding and winching.

"Optional Charge Indicator Light Function: Your Powermaster Alternator is designed to work as a 1 wire without any connections to the plug in. The function of the plug is to run a charge indicator (Idiot Light) only. This plug also does not serve as a hookup point for a voltmeter, or help charging at idle. This connection has no effect on charging performance." https://www.powermastermotorsports.com/alt1_gm_si.pdf

"Simply run a charge wire from the battery terminal on the alternator to the positive terminal on the battery. The one-wire regulator is a self-exciting regulator, meaning that it has sensing circuitry for alternator rotation. As the alternator starts to spin, this circuitry connects the internal voltage regulator to the battery and turns the alternator on. When the alternator comes to a complete stop, this same circuitry turns the alternator off.Powermaster early style Delco alternators will work either way - as a one wire or OEM style. The main difference between a one wire and an OEM is the method used to energize or turn on the alternator. An alternator using the OEM style is turned on with the ignition switch.

The one wire design is energized with a special sensing cicuit built into the internal voltage regulator. This circuit senses the rotation of the alternators rotor. The rotor must turn at sufficient speed to trip the circuit, starting the charging process. This turn-on speed is affected by several things and is typically higher with certain high amperage alternators. Once this circuit is tripped, the alternator will charge at all speeds, even very low ones, until the alternators rotor comes to a complete stop. At that point, the circuit will shut off and wait for the process to be repeated. What this means for the consumer is that in some applications the engine must be revved to 1200 or 1400 RPMs to turn the one wire alternator on. If the wiring harness is available and this characteristic is annoying, then Powermaster alternators can be plugged in like the stock unit and operated with the ignition switch." https://www.powermastermotorsports.c...tors_a.html#15

 

I have a 1988 22re Toyota Pickup I bought from fb marketplace a few months ago. The guy who had it before me swapped it to a late 80s gm alternator as well as adding a theft repellent kill switch. I’ve been driving it for the past two weeks perfectly fine until about 2 weeks ago it randomly killed itself while driving through the neighborhood. Threw a new battery as well as a new late 80s gm alternator from oreilys yet there is still no charge happening on the battery. Any help or advice is welcome. Thank you

 

sounds like you verified with an ohmmeter that it's not charging when the engine is running.

just for drill, did you have the old alternator tested at orielly's?

going back to original premise that it won't exite and charge when the bulb is burned out, did you lose any dash lights?

 

I did have the old one tested and he said it was bad. I just read a thread and it said many of these alternators are not fully rebuilt and just one part is replaced. I planned on taking this new one out and up to oreilys tomorrow afternoon to see if they sold me a dud.

I don’t have any dash lights beside when starting the vehicle it will have a check engine light until it idles. I also have an e brake light on when engaged other than that nothing.

Both times the battery has died I haven’t gotten a light come up on the dash so I assume the wires been unplugged or cut.

 

getting the replacement tested sounds like a good idea.

when you turn the ignition on, before starting the vehicle, there should be several dash lights on, including the charge light?

 

I recently installed the bracket and the same alternator however the pulley is too far forward on my truck, I'm assuming nobody else is having the same issue?

 

you used the trail gear alt mounting bracket?