3G Alternator Install: A How To

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

  1. Here is what Mr. Alternator (864)591-1066 has. A 130amp alternator complete with stator wire, short bolt, and with no exchange required. Mine came with the standard finish for $145.00 with shipping included. I received it in about four days. As you can see from the picture the new 3G is approximately the same size as the old one. The cooling fan has been moved to the inside.


    Required Tools:


    The other parts you will need can be bought at a local car stereo shop. They are:

    1. waffer fuse holder rated at 150amps

    2. 150 amp waffer fuse

    3. 10 feet of 4ga wire

    4. (2) ring terminals for 4ga wire

    5. (1) scotch lock (not shown)



    1. Disconnect the battery.

    2. Remove serpentine belt.

    3. Remove the (2) bolts that mount the old alternator to the bracket (Top is 9/16", Bottom is 5/8").

    4. Using a flat blade screw driver, remove the (2) electrical connections from the old alternator & remove the alternator from the car.



    1. Insert the new 3G alternator in the bracket and thread in the bottom bolt only.

    2. Check for interference with the bracket and grind bracket as needed

    3. Bolt the 3G alternator up and check to verify serpentine belt is still the right length.

    4. Mount the fuse holder.


    5. Run 4ga wire from the stud on the back of the 3G alternator to the fuse holder.

    6. Run 4ga wire from the other side of the fuse holder to positive side of solenoid.

    7. Splice the new stator wire with a scotch lock to the small wire on the big electrical plug.

    8. Plug in the small electrical connector into the 3G alternator.

    9. Reconnect the battery.

    10. Start it up and YOU ARE DONE !!!!!!
    tonyzz likes this.
  2. I like these write ups you put Roland69. I might have to go back and professionalize mine and clean it up some. Nice work.
  3. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects. You have a 4 gauge power feed wire, so you need a 4 gauge ground wire. The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges.
  4. Yup,don`t forget a new 4ga ground wire as well.
  5. i already have a 4gauge runnin from the ground on the block (stock batt ground) to the spot on the fenderwell that is the computer ground... is that sufficient?
    Ipaman likes this.
  6. I used one of the sway bar mounting bolts on the drivers side.
    This is a solid ground right to the frame.
  7. I dont know how effective it is, but 94-95's use a ground cable from the motor-side of the driver-side motor mount to the driver side [longitudinal] frame rail. I mirrored this on the pass side of the 94 for duplicity.

    For guys concerned with aesthetics (or like me, and have too much crap up top anyhow), this might be an alternative for a fox. Not as good as JR's methods, but better than nothing.
  8. My car has the ground at the back of the block to the firewall so do I still need to add another ground wire to the chassis?
    I plan on moving my battery to the trunk next whenever i have time and am going to put in a 3 point ground wire so eventually there will be a ground wire from the block to the chassis. So will the car be fine untill I do this?
  9. Do you have a 3g now?

    I would add a 4ga ground wire if you do.The fox body grounds are weak.

    I think many forget the 4ga wire,but I can`t recall any bad issues off hand.
    Still,the more grounds the better.

    Adding a ground wire is easy.
    bada$$92 likes this.
  10. is the stator wire necessary? I can use a small connector right?
  11. yes the stator wire is necessary.u can clip one off a car from the junk yard.
  12. FWIW a "Mega Fuse" and a "Mega Fuse" holder are cheaper than using a wafer fuse.
  13. i used a small spade connector on mine, didnt want to take another trip to go find one, works just fine.
  14. i cant get the connector on the the terminal thing...

    also, should the wire be as short as possible from the alt post to the fuse holder? (i.e. mounted where the air box is)
  15. most people ive seen run with the fuse around near the batterytray, me included.

    if youre using the spade connector on the stator, you may have tak a pair of pliers and squish it some if its too small, or stick a small screwdriver in it to spread it out some. do it a little at a time so you dont overshoot. in all reality the actual oem plug is the better option (it has plastic locks on to keep it in there), and this is just a workaround.
  16. I just installed mine, 170 amp kit 3g style, I did not install a 4G ground but to each his own. I have a 200 amp ANL style fuse and holder. You should laways but the fuse as close to the battery as possible. I routed my 4g power wire from the alternator up in front of the radiator along the same harness and zip tied it. Then I removed my battery and in the tray I drilled a small 1/2 or so hole on one side of the tray "in the recessed portion of it" and a hole on the other side. Slid the power wire through, installed the fuse holder and then slid the other side of the power wire through and installed it to the sylenoid. WORKS AWESOME and all hidden! I never even see the battery guage flinch!! Even with under drive pulley!
  17. Do you have any pics of your install? I would like to see what it looks likes.:nice:
  18. cool, well my battery is now in my hatch so it would be tough to get it close to that...lol

    but I plan on mounting it where the tray used to be under the hood
  19. which one is the stator wire?
  20. On a Mustang 86-93, the stator wire is the small white/black wire in the same plug as the two larger black.orange wires.

    Remove the negative cable from the battery for safety reasons.

    Black/orange wires get taped up out of the way and not used. Do not remove or mangle the plug on the end of the wires.

    Small 3 wire plug used as is, no changes. It plugs into the same connector on the new alternator.

    White/black wire on the plug where the Black/orange wires connect gets insulation stripped from it. Splice another wire onto it to make a Y. Solder the connection and use heat shrink tubing on it to cover the splice joint. Crimp a female 1/4" push on terminal on the new wire or use a connector from an old wiring harness.

    Plug the 3 wire plug into the alternator.

    Plug the white wire you spliced the into the little tab on the alternator.


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

    Starter solenoid wiring with a 87-91 5.0 Mustang


    Starter solenoid wiring with a Mini starter or 92-93 5.0 Mustang

    I ran the 4 gauge wire under the front of the engine next to the 4 gauge wire for the starter power feed.
    It came up the same path as the fuel injector supply lines, and gets bolted to the power output lug of the 3G alternator. The 125 amp fuse is mounted on a plastic panel bolted to the stock ignition coil mounts. One of side of the fuse has a 4 gauge wire connected to the battery side of the starter solenoid & the other to the 4 gauge power feed wire for the alternator.
    Reconnect the battery negative cable.

    Wiring is now finished. Check to make sure it is all neat and clean and everything is out of harms way. Start the car and check your voltage.

    I had some 1" silicone aircraft heat shield tubing that I fed the 4 gauge alternator power feed wire through and tie wrapped & clamped it in place with some aircraft cushion clamps. That provided the wire extra protection from road debris and rocks. Some heater hose could be used to do the same thing.

    I have an additional 4 gauge ground running from the power steering pump mount to the common chassis ground being pointed to in the photo.

    Picture courtesy timewarped1972 [​IMG]

    Apart from the grinding I did on the mount bracket, there wasn't much to it. Rather than just grind a notch, I ground the whole web back to the thick part of the bracket. It looks much more factory that way.

    For a 135 amp circuit breaker, see http://www.wiringproducts.com/135-amp-high-amperage-circuit-breaker.html price is $51.69

    For a 120 amp circuit breaker see Del City - Wiring Products and Professional Electrical Supplies price is $29.45

    Fuse holder from local NAPA dealer - Item#: BK 7821143 Price: $10.49
    Product Features: Thermal Plastic Holder For AMG Type Fuse Rated From 100 To 300 amp
    part numbers are 782 1143 (fuse holder) and 782 1137 (125 amp fuse) at NAPA

    See Parts-Express.com - Speakers, Speaker Building, Home Audio and Video, Pro Audio, Electronic Parts & Accessories PARTS EXPRESS, Speakers, Speaker Parts, Guitar speakers, Bass speakers, Woofers, Drivers, speaker upgrades and replacement speakers. Emine for the fuse & fuse holder.
    Fuse @ $3.90 each (need one) Parts-Express.com:150A Gold Plated Wafer Fuse | wafer fuses wafer fuse plates plate fuses fuse

    4 gauge black wire @ $1.95 a foot (use string to lay out routing & determine length) Parts-Express.com:4 AWG Black High Current Power Cable 1 ft. | amplifier install Power Wire power cable car audio automotive audio cable audio 4 ga powercable-41108

    4 gauge red wire @ $1.95 a foot (use string to lay out routing & determine length) Parts-Express.com:4 AWG Red High Current Power Cable 1 ft. | amplifier install Power Wire power cable car audio automotive audio cable audio 4 ga powercable-41108

    4 gauge ring crimp terminals (package of 5) $3.25. Parts-Express.com:DISCONTINUED 4 AWG Ring Terminal 3/8" Stud 5 Pcs. | solderless terminal ring terminal crimp connector solderless crimp crimp on

    3/4 “ Black heat shrink tubing, 4ft length, $3.56
    Parts-Express.com:3M 3/4" Black Heat Shrink Tubing 4 ft. | shrink tubing heat shrink wire management wire marker

    3/4 “ Red heat shrink tubing, 4ft length, $3.56
    Parts-Express.com:3M 3/4" Red Heat Shrink Tubing 4 ft. | shrink tubing heat shrink wire management wire marker

    Pre-fab 4 gauge cables with lugs already on the ends are available in most auto parts stores. Look for the starter switch to starter cables.

    Don't forget to trim the alternator mount bracket to provide clearance for the lager 3G alternator case. The first post on this string of posts will tell you more.
    See http://www.mustangcentral.net/tech/alternator.html for some excellent pictures of what you need to grind off the alternator mount bracket.

    3G tech data:

    See http://www.geocities.com/smithmonte/Auto/3G_130A_Alternator_Upgrade.htm - all the tech data you could ever want to know
    Mustang Central.net 130 amp alternator upgrade - excellent pictures of installation[/url]

    Attached Files:

    #20 jrichker, Jan 21, 2007
    Last edited: Sep 9, 2014