86 Bronco II Alternator Wiring

[The Slider]

There are 3 wires going to the alternator and 3 wires that go to the voltage regulator. Does anyone know what wires do what so I can test them??
I have a new alternator and battery and still won't charge. I pulled the harness and checked all the wiring and everything is good.

The Alternator has a built in Voltage Regulator.

Thanks!

 

[RonD]

You are changing from a 1G alternator to a 3G alternator

So you are going to remove the External Voltage regulator.
You need the 3 wire connector for the new alternator, it will have:
Yellow wire
Light Green wire
White Jumper wire

There should be a Larger wire that was connected to a Stud terminal on the original alternator, that will be connected to the Stud terminal on the new alternator, its called the B+ terminal, this is connected to the Battery Positive all the time, the main Charging wire, high AMPs

External voltage regulator will have a Yellow/white stripe wire from truck harness, that needs to be spliced to the Yellow wire on the new 3 wire connector.
This is the Monitor wire, it tells the internal voltage regulator the current system wide voltage, i.e. when you turn on the head lights, power demand goes up so voltage regulator increases AMP output of alternator.

There will be a Light Green/red stripe wire on the external regulator, that needs to be spliced to the light green wire on the new 3 wire connector, this is the ON/OFF switch for alternator, it only has 12v with Key ON

White jumper wire plugs into alternator's Field, it is a spade terminal next to the 3 wire connector, this monitors voltage output

Remove external Voltage Regulator and its other wiring

If you have a Carburetor and electric choke you will need to add a relay to active it with key on power, if Fuel injected then no electric choke

If you have an AMP meter instead of a Voltage Gauge in the dash it should still work

Any alternator's AMP output changes with engine RPMs, the Point of a voltage regulator is to maintain 13.6volts with engine running, 13.5-13.9v won't "cook" a battery, but it will keep it charged.
Right after startup you should see 14.5volts or higher, but under 15volts, this is the "fast recharge" since battery was just drained by starter motor.
Voltage should drop within a few minutes to under 14volts and remain there until engine is restarted
After voltage has dropped to 13.6v or so, turn on all the electrics in the vehicle, headlights, fan blower to high, dome light, ect.....
Voltage should drop for a second then voltage regulator should respond and voltage should return to 13.6v if that is what it was.
Raise RPMs, voltage should go up for a second but then come back to 13.6v.
These are tests that the voltage regulator is working, and all 3 Fields in the alternator are working

 

[The Slider]

My alternator has a built in regulator. 2 plugs one to the regulator on the back of the alternator and one plug on the side of the alternator. I don't have any wires attached to any studs. I have a Dummy Light for the amp. It is also fuel injected. I don't know if it is a G1 or G3 alternator. Probably G1 being just like the factory one that came with it.

Thanks!
Chaz

 

[RonD]

The "G" means generation, so 1G = First generation, just FYI, and 1G used external voltage regulator

2G were the first with internal voltage regulator, and were nick named “firestarter” and “flame-thrower”, so not a good "upgrade", if that's what you got

Most would get a 3G alternator if a 1G, or a 2G, alternator failed.

The charging system is self contained, not part of the vehicles wiring except for the ON/OFF wire, the light green wire.

The 2G and up alternators wiring might be "in" a main wiring harness for neatness but it only connects to the Battery positive cable, usually at the Starter Relay on the inner fender

It is grounded via its metal case

You can go here to see the different Ford alternator wiring: http://www.fuelinjectedford.com/page63.html

If you have 2 separate two wire plugs and an Internal voltage regulator then you most likely got a 2G, and if possible take it back and get a 3G

2 of the wires will be for B+, 2G had higher AMP output than 1G so Ford used two smaller wires, vs one Larger wire for B+, this was for the use with lower amp rated fusible links

But the voltage regulator connector should have 3 wires, even with 2G, counting the short white jumper wire.

Anyway look up 1G, 2G, and 3G wiring diagrams in above link, so see what you might have