3G Alternator Upgrade
A 3G alternator is a 130 Amp alternator that can be found in '94/95 5.0L Mustang GT's
The alternator is a substantial upgrade from the stock 60amp Bronco Alt.
What is needed from the Bronco:
- Intact factory wire harness
- Wiring schematic (Although you may figure it out by this page)
What is needed to wire the Mustang alternator:
- Alternator Plug. This can be had by getting one from NAPA for around $20.
- 1-Female spade connector (Solder type with heat shrink)
- 4-Butt connectors (Solder type with heat shrink) These will need to fit over the stud on the starter solenoid as well as the stud on the alternator.
- 8 Gauge wire (You may go larger but 8 gauge is the recommended minimum)
- 16 Gauge wire
- 1-120 Amp Circuit Breaker (Del City part #185120F)
- 1-12 gauge fusible link
- 1-18 gauge fusible link
- *Optional* 3/8"-16 Helacoil kit
Once all the parts have been obtained, let's get to upgrading............
Step 1: Remove alternator harness from the Bronco
Disconnect the battery. Unbolt the alternator and pull it up and remove the harness from the back. Remove alternator harness connection from the starter solenoid. Remove voltage regulator from the firewall. Unplug the alternator harness from the firewall connection.
Step 2: Prepare alternator harness for modification
Remove tape/covering from harness to locate all the wires within. The wires that need to be saved are the black/yellow stripe (10-12 ga), black (10-12 ga), and green/red stripe (16 ga). All others are no longer needed.
The items I removed were:
1) yellow (cut at fusible link),
2) orange,
3) white (stator/choke), and
4) the wire that had the insulation burned off????,
5) and the regulator. I cut the green/red stripe wire as close to the voltage regulator as I could.
Step 3: Prepare 3G alternator for mounting
I bought the alternator from an automotive store asking for a 94-95 Mustang alternator. To mount the alternator I did a few things to make things work better for me.
- Pull off the serpentine pulley so that you can install the v-belt pulley from the old alternator. DON'T INSTALL THE V-BELT PULLEY YET! I wanted the connectors to face the passenger side so that I wouldn't have wires underneath the alternator. To do this, remove the 3 long bolts that hold the front and rear case together. Separate the front case and rotate it so that the connectors will face the desired direction. (Hold the alternator as if it were mounted to ensure the connectors are the way you like) Re-install the bolts and now install the v-belt pulley from the old alternator. Do not use the old cooling fan as the 3G alternator has an internal fan for cooling. Check to ensure the pulley doesn't rub the case. You may have to install a spacer between the pulley and bearing to gain the spacing. I didn't need to but it was really close.
- This step is optional, however I wanted the alternator to be as easy to mount as the old one. The adjustment bolt hole on the 3G alternator is not threaded so you have a decision to use a nut and bolt or helacoil the hole to accept the original adjustment bolt. I opted to helacoil since the clearances are tight in the EB. The helacoil kit from NAPA was about $20. The hole is already drilled 3/8" so all that was needed was to tap the hole and install the helacoil.
- Mount the 3G alternator on the Bronco so that you can fit/cut wires for a nice and neat look.
Step 4: Make new alternator harness
In these steps you may want to lay the Bronco alternator harness in the truck to check wire lengths and routing. Keep in mind, this is the method I used to wire the alternator. You may find it better to do it differently as there are other ways to get the same connections accomplished.
- The black/yellow stripe wire on the Bronco harness will go to the 12 gauge fusible link. Connect the fusible link to the output post on the 120 amp circuit breaker.
- The black wire on the Bronco will go to the 12 gauge fusible link. Connect the fusible link to the positive post on the starter solenoid.
- The green/red stripe wire on the Bronco will go to the green/red stripe wire on the alternator plug.
- The yellow/white stripe wire will connect to an 18 gauge fusible link. Connect the fusible link to the positive post on the starter solenoid. (Another option is to connect the fusible link to the output post on the circuit breaker.) I chose the starter solenoid so I didn't have numerous connections on the circuit breaker post.
- The white/black stripe wire is connected to the single spade connector on the alternator.
- Connect a new piece of 8 gauge wire from the B+ post on the alternator to the input post on the 120 amp circuit breaker. Connect another new piece of 8 gauge wire from the output post of the circuit breaker to the positive side of the starter solenoid.
As you may see, the alternator is putting voltage both into the truck as well as to the battery (after passing through the 120 amp circuit breaker). The downfall to this method is the ammeter in the truck is no longer accurate. I have never been a big fan of ammeters and recommend a volt meter instead. By adding the wire from the circuit breaker to the starter solenoid gives a short line feed to the battery. You may chose to not wire the short line feed if you would like the ammeter to function accurately but this means all the power will be going through the Bronco's equipment before it runs back to charge the battery. Conversely, you may eliminate the black wire to completely eliminate the ammeter all together.
Step 5: Test
Hook up the battery and look for smoke! Get out your voltmeter and check the battery. It should be around 12.5 volts. Start the Bronco and check the battery again. It should now be 14-15 volts. The norm should be 14.2 - 14.7 from what I read. Now hook up all the electrical equipment you want as your Bronco can now handle just about anything you throw on it!!!! (Winch, lights, power inverter, etc)
If you really require a lot of power, you could substitute the added 8 gauge wire with something a little heavier such as 6 or even 4 gauge like I did. I've heard people going as big as 00 gauge. This may be overkill, but overkill generally doesn't hurt.
If you are wanting or needing even more amprage after this upgrade, companies such as PA Performance sells a 200 amp 3G alternator upgrade www.pa-performance.com