Electrical Alternator (91 Mustang GT & 89 Lincoln Mark VII)

Jhp84

Member
Mar 2, 2019
75
11
18
california
Picked up a 91 Mustang GT as a project car for my son and I work on. The mustang alternator (75 amp?) drains the battery overnight (draws 3.08 amps); figured it is the diode. Picked up a 100 amp from the junkyard from a 1989 Lincoln Mark VII. Had it checked at autozone. Told it failed. Going to have to rebuild one of the two alternators. Wondering if they are both G2 versions, and if it makes sense to rebuild the 100 amp alternator. Do I need to change harness? Add separate fused hot line? Will it fit without having to modify the alternator bracket on the Mustang?

Thanks, Jhp
 
  • Sponsors(?)


Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,568
7,821
224
Massachusetts
There are numerous 01-04 v6 mustang 6G alternators on eBay for $40 shipped or so. I wouldn't spend a dime on a 2G alternator given the abundance of 3G and 6G Alts
 
  • Like
Reactions: Jhp84 and jrichker

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
27,135
2,660
224
73
Dublin GA
@Jhp84


Mustang5L5 said:
There are numerous 01-04 v6 mustang 6G alternators on eBay for $40 shipped or so. I wouldn't spend a dime on a 2G alternator given the abundance of 3G and 6G Alts.
That's the best plan. The 6G supposedly does not require the alternator mount bracket to be modified.
Modifying the alternator mount bracket for a 3G is 10-15 minutes work with a rotary file and a drill or die grinder. Not hard to do, just be sure to clean up all the loose aluminum chips when you are done

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

Alternator wiring.






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


Starter solenoid wiring 92-93 model cars.


Fuse holder from local NAPA dealer - Item#: BK 7821143 Price: $12.99
Product Features: Thermal Plastic Holder For AMG Type Fuse Rated From 100 To 300 amp.

217813.jpg


I would use a maximum of 120-125 amp fuse for the output wire that connects to the starter solenoid. Fuses are slow blow so it would pass 130 amps for a continuous runtime without blowing

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.
 
Last edited:

Jhp84

Member
Mar 2, 2019
75
11
18
california
Thank you both for the recommendation on the G6. Taking my son to see if we can pull one from the junkyard (seem to be number of 01-04 on the website). While we are there, anything else we should consider to pick up for the swap?

On an unrelated note, would we be able to use the electric fan and radiator from the 01-04 on the 91?

Again, thanks. Good to be working together with my son instead of arguing over other things.
 

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,568
7,821
224
Massachusetts
Radiator no.

Fan really all depends on if it will fit and custom mounts. I'm using a 94-95 fan in my car
 

Jhp84

Member
Mar 2, 2019
75
11
18
california
No luck yesterday finding a G6 alternator in the junkyard. Heading over to another junkyard to continue our search for a G6 alternator for our project 91 Mustang GT. Any other vehicles/years from which we could grab an alternator that would fit, without having to modify the bracket (Taurus? Thunderbird" etc.). Thx, jhp
 

Blown88GT

Founding Member
Nov 13, 1999
1,681
313
124
Palm Beach Gardens, FL
Easy to tell 2G from 3G.
2G has external fan
3G & above have internal fan

I've had the original working 2G sitting in a box for 25 years.
Free to good local home.
 

Jhp84

Member
Mar 2, 2019
75
11
18
california
The clearancing for the 3G alt is minimal. 5-10 min with a grinder or even a dremel.


If you want the 6G I think it's 01-04 v6 stang only. The 4.0 sohc explorers might have a similar one.

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/332994839300

I'd just offer up $35-38 for this shipped with a 60'day warranty
Thanks for the suggestion. I guess it would be easiest to purchase, but my goal is to keep connected and learn together with my son about his project car before he finishes high school this year. Been a few rough patches between us these past years. Treks out to the junkyard give us a neutral place to chat without interruption, to shoot the bull...

Anyway, quick follow up question, what are the big differences between the 3G vs 6G, particularly for this vehicle (if any).

Hop
 
  • Like
Reactions: Mustang5L5

mikestang63

SN Certified Technician
Aug 27, 2012
9,821
6,603
204
In the garage
3G's are everywhere in s JY.

94-96 mustang
94-96 t-bird 3.8
95-96 windstar 3.0
93-96 e series vans f series truck w 4.9 i-6
3.0 taurus
94-96 cougar 3.8 v6
 

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,568
7,821
224
Massachusetts
Anyway, quick follow up question, what are the big differences between the 3G vs 6G, particularly for this vehicle (if any).

Hop
Case size mostly. The 3G are all mostly 130a. I believe the 6G is 110A

Clearancing is minor really. I have one and it was an easy install.

Great reason for heading to the junkyard. Good luck in your search and hope you have a great time doing it.
 

Jhp84

Member
Mar 2, 2019
75
11
18
california
Quick update. Field tested three 6G alternators at the JY. Two passed the diode test and both put out current when we spun the pulley with the impact drill. One, however, came to a fairly fast stop when we removed the drill. We figured the bearings were wearing out. So, we picked up the one from a 2003 Mustang.

Came back, and it fit in the bracket without a hitch. We will need to replace the regulator connector, as the 2G one doesn't fit. Presume we can cut it off and solder the one that we removed from the 6G at the JY. As for the 4 ga wire to the alternator output. if I understand correctly, we put a short run from the starter solenoid to a 125A fuse (which we mount to the sidewall? under the battery?) and then connect to the alternator, running the line between the radiator and the grill. Is that right? And, we simply forget about the other power connector (other than sealing). No need to worry about the two orange/black wires nor the white wire either?

Btw, new to this forum stuff. Noticed the water pump has fluid coming from the weep hole. Do I start another thread on the to get advice on that?

Thanks, you folks have been helpful and kind. Jhp
 

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,568
7,821
224
Massachusetts
Stator wire isn't used with the 6G

Need to solder the green to the green and yellow to the yellow on the regulator plug
 

Blown88GT

Founding Member
Nov 13, 1999
1,681
313
124
Palm Beach Gardens, FL
...

1. Came back, and it fit in the bracket without a hitch.
2. We will need to replace the regulator connector, as the 2G one doesn't fit.
3. Presume we can cut it off and solder the one that we removed from the 6G at the JY.
4. As for the 4 ga wire to the alternator output. if I understand correctly, we put a short run from the starter solenoid to a 125A fuse (which we mount to the sidewall? under the battery?) and then connect to the alternator, running the line between the radiator and the grill. Is that right?
5. And, we simply forget about the other power connector (other than sealing). No need to worry about the two orange/black wires nor the white wire either?

6. Btw, new to this forum stuff. Noticed the water pump has fluid coming from the weep hole. Do I start another thread on the to get advice on that?
...
1. https://alternatorparts.com/ford-type-3g-4g-6g-series-high-output-alternators.html
2. Correct
3. I assume so.
4. Correct
5. Correct
6. Replace water pump.
 

Jhp84

Member
Mar 2, 2019
75
11
18
california
1. https://alternatorparts.com/ford-type-3g-4g-6g-series-high-output-alternators.html
2. Correct
3. I assume so.
4. Correct
5. Correct
6. Replace water pump.
Ok, so let me follow up with a water pump question. When I grabbed the ill-fated alternator from the Lincoln Mark VII on our first trek out to the JY, I also pulled the water pump off of it. At the time I thought it would be prudent to snag it, just in case. Given that the alternator turned out to be the wrong size and defective (see picture), I am now wondering if I could use the water pump I picked up at that time. If not, from what other cars (models/years) could I pull a replacement water pump. Or, does it make more sense to get a rebuilt or new one?

[At the JY where we got the alternator from the Mark VII, we also pulled the radiator hood. Turns out the overflow container and its location is different in the Mustang. The Mark VII didn't have a sensor in the overflow. So, lesson learned for my son and I: Take pictures beforehand or know your own car better.

We also thought about grabbing the fuel rails and a couple of sensors, but we weren't sure if these would fit. Does it make sense to return to the first JY and get these as back up?]

Thx, Jhp
 

Attachments

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,568
7,821
224
Massachusetts
Hard pass on the JY water pump. Who knows how long it's been sitting and what's that's done for the internals.

I would just grab items as needed for now. The mark 7 motor does have some differences. The basic long block stripped down is the same, but items like assessories, and pullies and such do differ. Unsure about the fuel rail though.