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.
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.
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.
Cut the plug off your Toyota harness.
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.