ID89GT
10 Year Member
I did mine a few years ago when I had my 89, so if its going up still then its probably even more expensive now then it was when I did mine.
3G Alternator Upgrade - Remove Old Wires?
- Thread starter JasinC19
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Boydster
Active Member
To add to the cost of doing it yourself, plan on buying a crimper that will handle 4ga cable. If someone figures they can just use a vise and hammer on their 4ga alt cable... that's a plan to fail.
Boydster
Active Member
Hadn't thought of that. Mine is crimped and shrink'ed, but solder would have been a good idea to lock out moisture and corrosion...
txstang84
15 Year Member
+1...burnzomatic torch, and some flux core solder. All the terminals I did for the battery to the rear and 3G upgrade (done at the same time), have held up thus far. After pulling the engine, and removing wiring, I inspected all the lugs...they're still just as good as the day I put them together.
Blown88GT
Founding Member
txstang84
15 Year Member
you ain't even kiddin'!Here's the correct way to do the 3G wiring. Follow this, save money and it will be done the right way.
Stangnet 3G install sticky http://www.stangnet.com/mustang-forums/646825-3g-alternator-install-how.html#post6673702
The old wiring harness contains one yellow/white wire that is the voltage sense wire. It purpose is to measure the voltage drop between the alternator output and the body wiring buss. It will cause the alternator to increase its output voltage if there is a significant drop between the alternator output terminal and the body wiring buss.
That wire must be present for the alternator to work. For that reason, leave it in place when using a 94-95 Mustang 3G alternator. If your alternator is not a direct one for one swap with a 94-95 Mustang 3G alternator, that may not apply.
Here's the wiring diagram to show why...
Do not connect the black orange wires to the alternator: tape them up out of the way. 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.
Question about the yellow/white wire???
I am installing a 3g alternator and am running a new 4ga wire to the solenoid. I also have to replace yelloe/white wire and 18 ga fusible link, could i just save myself the run all the way back to the solenoid and just loop it to the screw post for the 4 ga wire on the alternator? they connect down the line anyways.
Great Thread!
The yellow wire is the sense wire that sees the voltage at the end point. It detects any voltage drop between the alternator output stud and the connection to the starter relay. It raises the output voltage slightly to accommodate any voltage lost in the wiring between the alternator output and the main electrical connection at the starter solenoid.
Ok, Ill run one back to the starter solenoid. Thank you for the reply and diagrams!
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