3G Alternator Install: A How To

Discussion in 'Fox 5.0 Mustang Tech' started by Roland69, Jul 3, 2006.

  1. In case this only pertained to the solenoid connection: As Jrichker noted, leave the OEM wires attached to the solenoid (you remove no wires from the solenoid for a 3G swap) but do NOT reconnect those same wire(s) at the back of the alternator. Doing it this way keeps the sense circuit active while not using the stock wires to carry alternator load.
  2. See here for how to build a factory style harness for a 3G conversion.
  3. I would also like to see a 3g how to and diagram for the 79-85 with external regulator.
  4. [​IMG]

    Use 4 gauge wire and a 125 amp fuse.

    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 a much current, so it needs to be 4 gauge too.

    The picture shows the common ground point for the battery & 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
  5. Hi all. I went the 3G route as well when my factory 75 amp unit died. I've read the posts many times but have a few quick questions.

    1) Where is the best place to mount the fuse holder? I`ve read that it should be close the the battery and I`ve read it should be closer to the alternator. Which one is it?

    2) Is it better to hexi coil the top hole of the alternator, or will the nut and bolt with washers way work just as well? One individual posted allignment issues with the belt when using the nut and bolt method.

  6. The fuse holder should go close to the battery. If the alternator fails with an internal short circuit, the idea is to limit the amount of cable that could be damaged by the heat created by the short.
  7. I fuse mine close to the power source (the alternator). The trade-off is that the heat will eat fuse holders.
  8. Thanks for the input. What about that top bolt?
  9. upgraded mine to 3g this past week

    First thanks to Jrichkter, I used those diagrams to make sense of this whole thing. I'm not a sparky by any means, so this was very helpful.

    I had fun trying to track down some 4 ga wire here....ended up finding it at Ace Hardware here in Colo. I found some welding wire, that has a thick rubber cover over a plastic liner....nice stuff. I paid $1.29/FT. I did have the pigtails from the 3g Alt I pulled off a Taurus with the alternator. Anyways, thought I'd add some photos of the Mega Fuse connection for those that haven't seen it yet.

    I found the mega fuse at CarQuest Auto.

    Attached Files:

  10. Folks,

    Sorry for the fairly simple, stupid question, but when you're running a 3g alternator, can you still pull the positive terminal from the battery? I only ask because we're running the 4g wire from the alternator to the battery. Would this cause the alternator to to stop "working"? Again, sorry for the stupid question. I'm still learning my newly acquired fox.

    Some background on the problem I'm having (also more background found here). A few weeks back, my fox died while at a gas station. They jumped me and got her running, but as soon as they pulled the charger off the battery, the car died. I ended up getting her towed home and ordered a 3g alternator (upgraded from stock). I'm confident I installed correctly, based on my readings from this forum thread (thanks). Though the car now starts (I changed the battery to 100% prior to upgrade to 3g), I'm still seeing that the aftermarket alarm, electric fan, and door chime aren't working. I tried to pull the positive terminal off just a few minutes ago, and the car stalled right out.

    Any help is much appreciated!
  11. Never, never disconnect an alternator from the battery with the engine running. The resulting voltage spike can damage the car's electronics including the alternator.

    Alternator troubleshooting for 86-95 5.0 Mustangs:
    Do all of these tests in sequence. Do not skip around. The results of each test depend on the results of the previous tests for correct interpretation.
    Changes in wiring for a 3G alternator are in red.

    Engine off, ignition off, battery fully charged.
    1.) Look for 12 volts at the alternator output. No 12 volts and the dark green fuse link between the orange/black wires and the battery side of the starter solenoid has open circuited.
    3G alternator: Look for 12 volts at the stud on the back of the alternator where the 4 gauge power feed wire is bolted.
    No voltage and the fuse for the 4 gauge power feed wire is open or there are some loose connections.

    2.) Look for 12 volts on the yellow/white wire that is the power feed to the regulator. No 12 volts, and the fuse link for the yellow/white wire has open circuited.

    Engine not running, ignition on, battery fully charged.
    1.) Alternator warning light should glow. No glow, bulb has burned out or there is a break in the wiring between the regulator plug and the dash. The warning light supplies an exciter voltage that tells the regulator to turn on. There is a 500 ohm resistor in parallel with the warning light so that if the bulb burns out, the regulator still gets the exciter voltage.
    Disconnect the D connector with the 3 wires (yellow/white, white/black and green/red) from the voltage regulator. Measure the voltage on the lt green/red wire. It should be 12 volts. No 12 volts and the wire is broken, or the 500 ohm resistor and dash indicator lamp are bad. If the 12 volts is missing, replace the warning lamp. If after replacing the warning lamp, the test fails again, the wiring between the warning lamp and the alternator is faulty. The warning lamp circuit is part of the instrument panel and contains some connectors that may cause problems.

    2.) Reconnect the D plug to the alternator
    Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see 2.4-2.6 volts. No voltage and the previous tests passed, you have a failed regulator. This is an actual measurement taken from a car with a working electrical system.

    Engine running, Ignition on, battery fully charged:
    Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see battery voltage minus .25 to 1.0 volt. If the battery voltage measured across the battery is 15.25 volts, you should see 14.50 volts

    Diagram courtesy of Tmoss & Stang&2birds

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

    Ignition switch wiring

    Fuel, alternator, A/C and ignition wiring

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

    Vacuum diagram 89-93 Mustangs

    HVAC vacuum diagram

    TFI module differences & pinout

    Fuse box layout
  12. If I recall correctly, with my old setup I stripped down the harness to just wires. Clipped the stock connector, soldered on the stator wire, and totally removed the the pair of old power wires. However, I left the yellow connected to the (dark green is it?) wire that went to the starter relay. Cleaned up the wires, taped up anything that looked like it needed it, loomed the wires up and put it back in the car. Then ran a 4ga wire from the stock battery ground to the EEC ground next to the battery, and ran the appropriate power cable. Worked fine for me, and cleaned up the install also.
  13. dumb question but here it goes...What cars can i take the 3g alt off of? And is there anything i can take of from car to ease my installation. like conectors...etc... thanks
  14. Copied from http://web.archive.org/web/20091027073848/http://geocities.com/smithmonte/Auto/3G_130A_Alternator_Upgrade.htm

    Here is a list of vehicles that have the 3G alternator, most are 130A, but some might be 110A:

    94-96 Mustang 3.8 V-6
    94-95 Mustang 5.0
    94-96 Thunderbird 3.8 V-6 (non SC)
    95-96 Windstar 3.0 V-6 (most are 3.8's)
    93-96 E/F series Trucks/Vans 4.9 L6*
    96 Sable 3.0 V-6
    94-96 Cougar 3.8 V-6

    *Probably the best one if you can get it (should be easy to find, too) is off the E/F series...this series uses a threaded top ear like the stocker on the Mustang....E/F series with threaded ear uses metric bolt. ALSO, make sure the E/F series is 130 Amps and NOT 95.

    The white/black stator slip on terminal wire is probably the only thing useful unless you are into tearing wiring harnesses apart. Be sure to read the first page of this 3G sticky for wiring and alternator mount modificatiion information.
  15. I just tested the green from the D connector and I get +/- 7 volts. could that have to do with a no charge? Got the alternator tested at autozone and passed
  16. This thread is for 3G installation questions and problems. If you are having alternator problems not related to the installation of a 3G alternator, please create your own thread.
  17. sorry,

    I have an alternator from a 95 mustang gt to install but am worried about it not getting a charge signal from the connector that will stay unchanged
  18. I wanted to point out a few things about the '86 wiring that is different from the newer cars (of course... PITA '86...). I wish I could explain it better (and maybe someone more knowledgeable can speak up) but I just don't understand alternator wiring all that well.

    First off, the regulator plug on the '86 does not have the white/black wire, only the red/green and yellow/white wires.

    There is also no stator wire (white/black) coming off the power plug (the other plug with the orange/black wires).

    PA Performance offers a regulator plug adapter specifically for installing 3G alternators in '86s. It's something like $12, and makes it real easy. It is a typical 3-wire plug with a factory snap-plug already installed on the white/black wire and a resistor on the red/green wire. I do not know what size resistor it is (forgot to look at the color bands before I shrink wrapped it) or what exactly it is there for, but it is my understanding that SOMETHING will not work right on the '86 if the resistor is not included on the red/green wire. Haha. Maybe someone can chime in on this?

    Here is a picture of the original '86 plug and the new PA Performance plug.


    Here is a picture of the stock '86 power plug. Sorry about the poor quality.

  19. I'm in the middle of doing my 3g conversion as it seemed pretty straight forward until I looked at my connectors and I don't have the third wire (stator) wire like nikwoaC just referred to on the 86 and I'm stuck. Can anyone help me out with what to do with the wiring as both of the stock plugs are different than those mentioned!?