Fox Battery Light

Rxzm said:

connect one of the 10g wire into the new alternator but the other wire had no input inside the alternator so I just left it hanging out.

Click to expand...

You must be looking for ways to burn up your Mustang. Why would you think that one wire would be sufficient when the original, lower output alternator used 2 wires ?

See the proper way to do it below...

A 4 Gauge is the minimum recommended wire for the output of a 3G, 130 amp alternator.
Wire size current table:


Here is the reasoning behind using only a single 4 gauge fused power feed to the alternator. If you use the two 10 gauge black/orange wires in addition to the 4 gauge wire, you have two fused power feed paths. The total current capacity of the wiring is the sum of the fused paths. The 4 gauge path is fused for 125 amps, and the two 10 gages wires are fused for 60 amps. That is a total of 185 amps, which exceeds the capacity of the alternator. Overload can occur without the fuses blowing, damaging the alternator.

The worst case scenario is that the alternator develops an internal short to ground resulting in a catastrophic failure. The initial short circuit surge current is limited by the resistance of the wiring. The current in a parallel circuit divides up according to the resistance of the branches. If the 4 gauge fuse opens up first, the two 10 gauge black/orange wires will be carrying the short circuit surge current. Depending on the time lag of the fuse links, they may open up before a fire starts or they may not.



Any car that has a 3G or high output current alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects. The 3G has a 130 amp capacity, so you wire the power side with 4 gauge wire. It stands to reason that the ground side handles just as much current, so it needs to be 4 gauge too.


http://www.stangnet.com/mustang-forums/threads/3g-alternator-install-a-how-to.646825/#post-6673702

Alternator wiring.






If you have a 3G alternator, the white/ yellow wire is critical to proper operation. It is the voltage sense and regulator power lead that picks up the difference in voltage at the alternator output stud and the connection point at the starter solenoid. If you cheat and run it directly to the alternator output, it sees the voltage at the alternator output stud. It does not see the voltage at the starter solenoid connection point where it feeds power to everything else. You may have a voltage drop in the wiring between the alternator output stud and the connection to the starter solenoid. Thus you may have low voltage or less than the standard regulated voltage at the starter solenoid connection point. This makes for low voltage throughout the rest of the car: everything operates at less than full efficiency.

Starter solenoid wiring 86-91 model cars.

Connect the fused 4 gauge wire to the alternator and the battery side of the starter solenoid.


Starter solenoid wiring 92-93 Model cars.

Heavy gauge power wire should fix it

To add a #4 ground where exactly does each end go? Like where on the block and chassis?

What I do is a heavy duty charge wire from the alt to the solenoid. And a heavy duty ground from the fender where the pcm grounds by the battery. Then I double check the block to firewall

doesn't anyone read the tech stickies? This is a new one to me- hooking up only 1 of the stock power wires, that is already a fire hazard with two wires.