Engine Question on 3G Alternator.

Discussion in 'Fox 5.0 Mustang Tech' started by James.Little, Jan 9, 2013.

  1. Could you tell/show me what the OEM charge cable, and sense wire look like/located? Im not familiar with those names, as far as what they look like, and are located at...
  2. I haven't removed any cables from the old 2G alternator, so does that mean I am good to go? I have spliced, soldered, and shrink wrapped the yellow and green wires, I seriously do not want to removed all that unless necessary. Also jrichker, thanks for the informative post!
  3. I don't have a pic of them. The charge cable is blk/orange and the sense wire is yellow. On the reg, the sense wire is labeled A if you want to trace it from the far end.
  4. Any particular reason you chose a 200 Amp Fuse, that seems kinda like overkill?
  5. Yeah it is. The only reason why is because I saw a kit on American Muscle and they had a 200amp fuse with it. I step it down to 150, which is still too high, but that is all they had. I really should pop in a 90amp fuse.
  6. If you are running a 130 amp alternator why would you run a 90 amp fuse. Try a 135 but the 150 should be fine.
  7. I have a 125 Amp fuse in mine.
  8. 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.

    The picture shows the common ground point for the battery , computer, & extra 3G alternator ground wire as described above in paragraph 2. A screwdriver points to the bolt that is the common ground point.

    The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
    Picture courtesy timewarped1972

    Correct negative battery ground cable.
  9. I think it is a 160 amp alternator. The reason why is because I am not running the alternator at 100%, which would be 160amps, but I am running it about 60% which is about 95amps, I think. This holds true for all fox mustangs with a 3g alternator, unless you change to a smaller pully to create more RPMs.
  10. The amp/alternator output is going to depend on

    1. what size crank and alternator pulley you have
    2. what rpm range you spin the alternator

    General rule is the alt should spin about 2-2.5 x the crank speed. Still what is the point of popping a 90 amp fuse when you have an alternator that is capable of 160 amps. By having a 135 or 150 amp fuse you are still below the alternator output but have the amps to run things like a stereo, efan, on top of your A/C, lights, etc.
  11. When I say 60%, I am talking about absolute maximum RPM. The amp rating on 4 gauge wire is about 90amps. It is a extra precaution.