FYI FORD MustangSteve's Ford Mustang Forum » Finished the 3G alternator upgrade today on my fox 5.0

MarkinSC · 7/06/2013 7:58 PM

Ran into a few snags along the way. But its finally done, and I have over 14 volts at idle, even with the headlights on. The stock 75 amp 2G alternator is now a trunk road spare. Getting closer to making this car Bash trip capable. A few weeks ago I removed the march underdrive crank and wp pullies and went back to stock pullies. It definitely helped improve the charging system at idle, but still not ideal. So the 3g upgrade is worth it .

For anyone thats interested in the parts list and price for this project on their 5.0:

(1) 94 Mustang GT 130 amp 3G alternator, ( ebay seller reconditioned for $75.00) Reconditioned alternators at Napa etc, run around $170 - $230 and require a core deposit, which my 2g alt does not qualify since its not the same alternator that I was buying.

(1) stator wire connector, ( from late model restoration for $6.99)
http://www.latemodelrestoration.com/item/LRS-14290C/94-04-Mustang-Stator-Plug

(1) 4 gauge ground cable 12 inches $5.99 at autozone

(1) 4 gauge starter switch cable, 18 inches, ( battery terminal to megafuse holder) $5.99 at autozone

(1) 4 gauge starter switch cable, 60 inches ( megafuse holder to alternator batt terminal) $11.99 at autozone

(1) wireloom roll, split wireloom, 3/8 size, $8.99 at walmart ( cover the positive cables that run from megafuse holder to battery, and megafuse holder to alternator)

(1) 4 gauge battery cable, 12 inches , (battery positve post to the starter solenoid). $5.99 at Autozone

(1) Mega fuse holder ( Napa $10.49, Part Number: BK 7821143)

(2) Mega fuse, 125 amps, ( napa, $6.49 each x2, one for a spare, $13.00 Part Number: BK 7821137)

(1) 3/8 bolt 2 inches long with 2 flat washers, 1 lock washer, 1 nut ( to secure alternator top hole to bracket) from Lowes. Approximately $2.00

(1) 5/16 hex bolt 1 1/2 inches long ( used to replace the stock bolt that came with the new 12 in battery cable so that i had some extra threads available to add the new charging cable directly to battery post.

(1) Longer serpentine belt napa part number: NBH 25060910 ( 91.68 inches long) stock belt is 90.5 inches long and would not reach with the new larger pulley that came on the new 94 mustang gt alternator. Price $21.49

(1) Interlock connector - to connect the new stator plug to tap into the existing stator wire on the original harness.

For anyone thats interested in the Prep work required for this project:

Where to mount the megafuse holder: Find a location to mount the megafuse holder where the cable length is ideally 12 inches long but not exceed 18 inches from either the starter solenoid bat post or the battery positive post. The mega fuse must be located close to the battery, recommended length is 12 inches from battery/solenoid and not to exceed 18 inches. I took out the battery, and the battery tray, and mounted the mega fuse holder on the frame directly under the battery tray to the right of the power steering hose bracket. There were two holes already in the frame that lined up perfectly with the holes in the megafuse holder. Two screws to secure it.

Where to mount the charging wire: I decided to connect it to the battery pos terminal instead of the solenoid bat terminal because its over crowded already to the point where I couldnt get another wire on there anyway. I tried and could not get the nut back on. I also decided to connect it to the battery positive post because I could be within the 12-18 inch cable length spec. I would have had to use a longer cable like 24-32 inches if i wanted to connect it to the starter solenoid.

Modify the alternator bracket. Had to notch out a section of webbing for the 3g alt to fit, and also notch out a section along the bottom side of the alternators top mounting hole so that the alternator case will clear that top mounting hole. Takes some time with a dremel to either cut away or grind away the metal. When grinding, use some wet towels to catch the metal shavings that fly everywhere.
Modify the alternator: On the back of the alternator is the batt post terminal which has a piece of plastic surrounding it so that the wire lug of the new charging cable fits directly between this round plastic, so that the wire lug doesnt make contact with the metal case. But the battery starter switch cable that is used to connect the battery to the alternator is too wide to fit onto that alternator bat post terminal with that plastic in the way. The cable will not sit flush against the alternator. The cable is too wide to sit between the two half round peices of plastic. With a razor blade, I cut away a notch on one side of the plastic so that the new charging cable would be able to rest flat onto the back of the alternator. If you don't remove this plastic, then the new charging wire would not rest flat against the back of the alternator and would not be able to secure it with the nut.

Modify the alternator again: the bottom mounting hole on the alternator was a smaller diameter than the long stock bolt that was removed from the 2g alternator . I had to get a drill bit and ream out the bottom mounting hole so that I can reuse the original stock long bottom mounting bolt.

Find a spot for the new ground cable. I removed the bolt on the ac/ps bracket and secured the new ground cable on one end there, and the other end to the driver side inner fender area near the windshield washer reservoir where there is an existing small ground wire secured there.

How to route the charging wire. The charging wire needs to connect the alternator to the megafuse holder near the battery. I did not want to run a long live wire from the starter solenoid , under the battery, up the side of the radiator, along the top of the radiator, and then around the side of the passenger fender to the back of the alternator. I would have needed a 90 inch wire. Instead I routed it underneath the oil pan alongside the other existing wiring harness and came up near the back of the alternator, and was able to user a shorter 60 inch wire. The wire is wrapped in the split wireloom for extra protection and secured to the existing wire loom wires via zip ties.

Modify the wiring harness: There are two ways to go. Use the entire 3g wiring harness connectors from a donor vehicle and splice it into the existing harness, OR, simply splice a new stator wire onto the existing 2g wiring harness. I opted to just splice on a new stator wire onto the existing wiring harness using an interlock connector. Of the original wiring that was connected to the original 2g alternator, there were two connector plugs. One connector is simply connected directly onto the new 3g. The other connector does not get connected to the new alternator and is taped off, but not removed from the car since the other end of the wires are needed to remain connected. The new stator wire is spiced into white/black wire that is on that disconnected connector plug that is not used, and this new stator wire plugs directly into the new 3g alternator.

Alternator pulley? For some reason, I needed a longer serpentine belt than the stock belt. My 2g alternator had an underdrive pulley on it which is smaller than the stock pulley. I am not sure if the stock 2g pulley is smaller or the same size as the 3g pulley since I didnt have one to compare. All i do know is that my options were either to get a longer serpentine belt, or take both alternators to autozone and have them take off the underdrive pulley from the 2g alt and put it on my new 3g alternator. I figured that if i ever need to reinstall the old alternator, it needs to have the smaller underdrive pulley on it to keep it charging at idle.

I'll try to add pics later.

Last edited by MarkinSC (7/06/2013 8:14 PM)

wsinsle · 7/06/2013 8:42 PM

Nice write up Mark. Is that the small case 3G, if so do you have the ebay link.

MarkinSC · 7/06/2013 9:46 PM

wsinsle wrote:
Nice write up Mark. Is that the small case 3G, if so do you have the ebay link.

http://www.ebay.com/itm/FORD-MUSTANG-ALTERNATOR-REMAN-5-0L-1994-1995-/120991503872?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1994|Model%3AMustang|Submodel%3AGT&hash=item1c2ba7d600&vxp=mtr

Here is the link of the ebay seller that I bought the alternator from. i think this is the large case since its 130amps. I read that that small case were 95 amps. don't quote me on this. I really am unsure about how to tell a small case vs large case.

there are sellers on ebay and aftermarket like PA etc that make small case 3g alternators with the higher amps such as 130 or even higher. I searched ebay for a 94 mustang gt alternator and found a stock alternator that was reconditioned. so it is possible to find small case alternators with the higher amp rating, but their not the stock alternators without modifications. Also some of these ebay sellers and aftermarket sellers have different wiring instructions such as the 1-wire alternators. I decided against going that route. so be informed that you will find 3g alternators with different wiring hookup and instructions than those that I posted. I wanted to be able to walk into any parts store in the usa and ask for a 94 mustang alternator and be able to get it the same day, and hook it up if I need to on the road. These specialty alternators from PA or other aftermarketers would require ordering it from them again online, and wait for it to be mailed, which is hard to do when on the road.

i also wanted to be able to hook up my old alt if needed in a pinch.

Last edited by MarkinSC (7/07/2013 6:49 AM)

MarkinSC · 7/07/2013 7:04 AM

ON a side note: I would recommend making sure you travel with a 1/2 inch breaker bar with a 1/2 inch 18mm socket if you ever have to replace the serpentine belt on the road. also recommend having spare serpentine belts of different lengths just in case you need to bypass something like ac or ps or smog pump. 'And know in advance what length belts you would need. also carry a spare 125 mega fuse. If ac compressor locks up or the smog pump locks up, you will need to bypass it with a different shorter length belt. Also stock lengths may not work for you if you are running underdrive pullies. I've learned how to read napa part numbers on the belts. the stock belt was part number that ended in 0905 which meant 90.5 inches long, so i searched thier website for 0910 part number and it was 91 inches long which is what i needed.

MS · 7/07/2013 10:54 AM

I have an alternator like that going on the F-100. Can you explain why the huge fuses are necessary? How were they wired up on cars they originally came on? I really do not want to run a whole bunch of huge wires if not required.

Alan · 7/07/2013 11:13 AM

On the fuses, how big is necessary to pull a mini starter on a 302? I had a 100 amp in a fuse holder and it blew instantly when I cranked the starter. I have it between the battery and the relay.

Last edited by Alan (7/07/2013 11:14 AM)

wsinsle · 7/07/2013 12:19 PM

The large fuse is usually placed between the alternator and battery, not battery and starter. The fuse is used to protect the alternator. I figure the train of thought is this, with he moving parts in the alternator it could develope an internal short. With the heavy wire they use to connect these larger alternators, the battery could supply a lot of amps to the short inside. This could result in a nasty fire. The fuse is to protect against that. As far as how big a fuse between the battery and starter I have no idea. It depends some on how big the motor and how much compression. I would say trial and error, but hat could get expensive.

MS · 7/07/2013 2:03 PM

Have never heard of using a fuse between battery and starter. That would have to be a huge fuse with up to 1,000 Amp cranking capacity of some batteries. The fuse would be the ignition switch.

As far as protecting the alternator from internal short powered by the battery, you may have a point, but it is no more than the existing alternators that had no such protection. I think I will take that risk and not have all the extra wiring.

GPatrick · 7/07/2013 2:43 PM

A fusible link is often used on the alternator circuit as well as the main source to the ignition swith. They are safe when installed properly but when buried deep in some harnesses or on certain fiberglass bodies they can create a fire hazard. Of course millions of cars had links but the big fuse and or relay companies will often show a fancy car burned to the ground because of a fire caused by a fusible link. I will use fusible links on my wiring as I think on a well installed system they are perfectly safe, cheaper, and less visible.

Glens 1965 50 · 7/07/2013 2:59 PM

Alan wrote:
On the fuses, how big is necessary to pull a mini starter on a 302? I had a 100 amp in a fuse holder and it blew instantly when I cranked the starter. I have it between the battery and the relay.

There is a great book on how to run breakers on your main power feed to your starter. This is normally done when you relocate the battery to the trunk and want to keep a large gauge wire for the charging system. Check out Tony Candela's book "Automotive Electrical Performance Projects" ISBN #978-1-934709-55-9. Also check him out on YouTube, just search Tony Candela.

You will need roughly two 200 amp breakers in parallel to make it work.

Nice write up MarkinSC.

MarkinSC · 7/07/2013 4:25 PM

MustangSteve wrote:
I have an alternator like that going on the F-100. Can you explain why the huge fuses are necessary? How were they wired up on cars they originally came on? I really do not want to run a whole bunch of huge wires if not required.

I wish I was an electrical engineer to explain it like it was coming from my brain, but I did alot of reading on this 3g upgrade, and all i can do is regurgitate all the different articles I read.

3g Alternator can produce up to 130 amps. A 4 gauge wire is capable of handling 136 amps so a 4 gauge wire is used to connect the alt to the battery. If you use a 4 gauge power wire, then you also need a 4 gauge ground wire as well. The fuse amperage to use is determined by the gauge of the wire that is being used that it has to protect. a 125 amp fuse will protect a 4 gauge wire. The fuse has to be near the battery although i read that it should be closest to the power source which is the alternator, but amongst that argument, the consensus was the fuse needs to be closest to the battery, and the shorter the distance from the battery, the better. so i read that it should be ideally 12 inches from the battery but no longer than 18 inches.

When retrofitting a 130 amp alternator in a fox mustang that originally only had a 75 amp alternator, the stock wiring can not handle 130 amps safely. The stock fox wiring utilized 2 individual orange/black power feed wires going back to the battery. Each of the 2 power feed wires are 10 gauge and merge to a single 14 gauge fusible link near the starter solenoid and then onward to a 4 gauge wire to the battery positive post . 10 gauge wire is rated to 55 amps. If the demands on the charging sytem are greater than 55 amps, the fusible link is supposed to protect it.

On the 94 mustang, a single 6 gauge power feed wire is used and they used 2 12 gauge fusible links.

Here are some of the internet articles i have read on this subject:

. http://home.comcast.net/~smithmonte/Auto/3G_130A_Alternator_Upgrade.htm

http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.mustangcentral.net/tech/alternator.html

http://www.stangnet.com/mustang-forums/threads/3g-alternator-install-a-how-to.646825/page-4

midnite · 7/08/2013 10:55 AM

You did well on the swap! There is a guy on corral.net that sells the whole wiring 4ga, fuse and the connectors to tap the stator wire kit for around $40 which is a decent deal, he also includes the required top bolt and nuts for the new alternator.

On my '90 GT I cut off the factory "D" plug, tapped the white wire into the new stator plug, and put ring terminals on the original black/orange wires and connected them with the new 4 gauge wire to the alternator. There is debate on whether or not you need to reuse the black/orange wires but they always remain hot so they at least need to be covered, common thought seems to be that it isnt hurting anything to connect them to the alternator since the majority of the power will go through the 4 gauge wire anyways. In the past I have just sealed them off and not noticed a difference.

Did you connect your 4 ga power wire to the battery? I have always connected it to the solenoid on the fender

I got my alternator on rockauto for $100. Brand new TYC for a 94 mustang 5.0, no core charge. Seems to be a nice peice at a good price! I also am running a slightly larger belt, the 3G pulley is bigger and doesnt interchange with the 2G pulley. Ive been debating buying one of the march kits that is supposed to overdrive the alt and underdrive the crank and wp, but not so sure its really worth it

Last edited by midnite (7/08/2013 10:57 AM)

MarkinSC · 7/08/2013 2:29 PM

midnite wrote:
You did well on the swap! There is a guy on corral.net that sells the whole wiring 4ga, fuse and the connectors to tap the stator wire kit for around $40 which is a decent deal, he also includes the required top bolt and nuts for the new alternator.

On my '90 GT I cut off the factory "D" plug, tapped the white wire into the new stator plug, and put ring terminals on the original black/orange wires and connected them with the new 4 gauge wire to the alternator. There is debate on whether or not you need to reuse the black/orange wires but they always remain hot so they at least need to be covered, common thought seems to be that it isnt hurting anything to connect them to the alternator since the majority of the power will go through the 4 gauge wire anyways. In the past I have just sealed them off and not noticed a difference.

Did you connect your 4 ga power wire to the battery? I have always connected it to the solenoid on the fender

I got my alternator on rockauto for $100. Brand new TYC for a 94 mustang 5.0, no core charge. Seems to be a nice peice at a good price! I also am running a slightly larger belt, the 3G pulley is bigger and doesnt interchange with the 2G pulley. Ive been debating buying one of the march kits that is supposed to overdrive the alt and underdrive the crank and wp, but not so sure its really worth it

I read NOT to connect those black/orang wires AT ALL. You are creating 3 paths for the current to go: the 4 gauge AND both black/orange wires which only have a small fusible link to protect them. In one of those articles I posted it addresses that issue. I know they are live, but they are to be taped up and moved to the side.

I connected right to the battery positive terminal. The starter relay post is overcrowded as it is.

I took off the march underdrive pullies that give you a smaller diameter crank pulley, and a larger diameter wp pulley. Created too many issues for me with charging, ps growling at idle making a turn, and ac not charging . Not worth the 6-8 hp at all in my opinion.

midnite · 7/09/2013 11:06 AM

MarkinSC wrote:
midnite wrote:
You did well on the swap! There is a guy on corral.net that sells the whole wiring 4ga, fuse and the connectors to tap the stator wire kit for around $40 which is a decent deal, he also includes the required top bolt and nuts for the new alternator.

On my '90 GT I cut off the factory "D" plug, tapped the white wire into the new stator plug, and put ring terminals on the original black/orange wires and connected them with the new 4 gauge wire to the alternator. There is debate on whether or not you need to reuse the black/orange wires but they always remain hot so they at least need to be covered, common thought seems to be that it isnt hurting anything to connect them to the alternator since the majority of the power will go through the 4 gauge wire anyways. In the past I have just sealed them off and not noticed a difference.

Did you connect your 4 ga power wire to the battery? I have always connected it to the solenoid on the fender

I got my alternator on rockauto for $100. Brand new TYC for a 94 mustang 5.0, no core charge. Seems to be a nice peice at a good price! I also am running a slightly larger belt, the 3G pulley is bigger and doesnt interchange with the 2G pulley. Ive been debating buying one of the march kits that is supposed to overdrive the alt and underdrive the crank and wp, but not so sure its really worth it
I read NOT to connect those black/orang wires AT ALL. You are creating 3 paths for the current to go: the 4 gauge AND both black/orange wires which only have a small fusible link to protect them. In one of those articles I posted it addresses that issue. I know they are live, but they are to be taped up and moved to the side.

I connected right to the battery positive terminal. The starter relay post is overcrowded as it is.

I took off the march underdrive pullies that give you a smaller diameter crank pulley, and a larger diameter wp pulley. Created too many issues for me with charging, ps growling at idle making a turn, and ac not charging . Not worth the 6-8 hp at all in my opinion.

I just remembered that I was having issues with the ring terminals coming off so I have bypassed the black/orange wires, I think you are right that this is a better way to do it. I agree the starter post is overcrowded though I had a good amount of room on mine

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» Finished the 3G alternator upgrade today on my fox 5.0

7/06/2013 7:58 PM #1

Finished the 3G alternator upgrade today on my fox 5.0

7/06/2013 8:42 PM #2

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/06/2013 9:46 PM #3

Re: Finished the 3G alternator upgrade today on my fox 5.0

wsinsle wrote:

7/07/2013 7:04 AM #4

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/07/2013 10:54 AM #5

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/07/2013 11:13 AM #6

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/07/2013 12:19 PM #7

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/07/2013 2:03 PM #8

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/07/2013 2:43 PM #9

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/07/2013 2:59 PM #10

Re: Finished the 3G alternator upgrade today on my fox 5.0

Alan wrote:

7/07/2013 4:25 PM #11

Re: Finished the 3G alternator upgrade today on my fox 5.0

MustangSteve wrote:

7/08/2013 10:55 AM #12

Re: Finished the 3G alternator upgrade today on my fox 5.0

7/08/2013 2:29 PM #13

Re: Finished the 3G alternator upgrade today on my fox 5.0

midnite wrote:

7/09/2013 11:06 AM #14

Re: Finished the 3G alternator upgrade today on my fox 5.0

MarkinSC wrote:

midnite wrote:

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» Finished the 3G alternator upgrade today on my fox 5.0

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Index » FYI Ford, Classic Mustang Tech Discussion » Finished the 3G alternator upgrade today on my fox 5.0

Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

wsinsle wrote:

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

Alan wrote:

Re: Finished the 3G alternator upgrade today on my fox 5.0

MustangSteve wrote:

Re: Finished the 3G alternator upgrade today on my fox 5.0

Re: Finished the 3G alternator upgrade today on my fox 5.0

midnite wrote:

Re: Finished the 3G alternator upgrade today on my fox 5.0

MarkinSC wrote:

midnite wrote:

Index » FYI Ford, Classic Mustang Tech Discussion » Finished the 3G alternator upgrade today on my fox 5.0

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» FYI Ford, Classic Mustang Tech Discussion
» Finished the 3G alternator upgrade today on my fox 5.0

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» FYI Ford, Classic Mustang Tech Discussion
» Finished the 3G alternator upgrade today on my fox 5.0