Alternator rebuilding

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My all time favorite vehicle is our 1969 Shelby GT500
What year and what is the current alternator amperage output? If this alternator has been in use for a while, and/or you truly need a higher amperage output, especially at low engine RPMs, it may be worth getting a new or high quality rebuilt unit as opposed to just replacing the front and rear bearings. If you choose to replace the bearings be sure to at least look at the brushes and replace if they are worn appreciably. I tend to rebuild vs replace, and because the alternators I had were 43 amp or so units, I opted to rebuild and replace the replace the rotors with rotors with more windings (increasing the amp output), or you could replace with a high quality new unit with higher amp output (for me, with all my electrical items running, I need at least 42 amps, but I need that at 1,500 engine RPM, not at 2,400 RPM. In both of our 73 mustangs that meant upgrading to get rotors that produces 65 amps or more. Now they keep up with the electrical demands I have (dual electric cooling fans, A/C and blower fan, gps/backup camera, DashCam, cell phone charging, ignition system, convertible top motor with the vert, and some other minor draws.

I did purchase a new alternator for one of the Mustangs and decided to rebuild with the rotor upgrade instead. I have opted to hold onto the new alternator in case I may ever need it, which is doubtful. I checked my receipts and ascertained I have a new Duralast Gold 100 amp alternator with side terminals (for our 73 Mach 1), model #7705-9N. If you have a rear terminal alternator this alternator will work, but you will need to get the appropriate wiring sub-harness for the correct connectors to the side terminal socket for Field and Stator terminals. These currently sell for $179.00, plus core, shipping, and sales tax. I am not desperate to sell it, but with the kind of rebuilds I did on our two 73 Mustang alternators (mostly to boost their output) I doubt I will need the new Duralast unit for a very long time, of ever. If interested shoot me an offer. If there are no takers I will just hang onto it. I purchased it late October, 2020, and it has been left in its box all this time, never used or installed.

 
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Hemikiller

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My mustang is a 1972. It puts out 14 volts but the bearing is growling bad.

Rock Auto has the bearings and brushes for good prices. I'd disassemble your alternator first to make sure you get everything you need. Don't want to have it apart and find you need a brush holder or other component.

1663607964988.png
 
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I was not having any problems with mine but I decided to install a bearing kit and rebuild myself.
Luckily those early alternators are fairly easy to work on and rebuild. Back when I worked at a Ford dealership I used to irritate the Parts Manager (not on purpose, I liked him. I even paid for this post-funeral expenses for his widow, without telling her I was going to do that. He was an honorable man and fellow veteran), because I did not replace alternators with complete new or rebuilt units. I would order the various internal parts needed, like front and rear bearings, brush and holder assembly, diodes, and a rotor if the contact points for the brushes were noticeably worn (or if the rotor had an open circuit). They did not take much more than that, and they always ran great afterward, especially when I would replace the rotor, which was always the rotor with the highest amperage rating I could get. No half steps for me! Those were fun times (70s and 80s)
 
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I agree 100% mrgmhale. The 70s and 80s were fun and great times. I met many interesting people, customers, shop personnel, and many from the Mother Ship (Ford Motor Company).
I had a great relationship with our shop techs. They knew they needed us to make a decent living. At the same time, even though I had fantastic retail and wholesale business accounts, I knew I needed them for good shop sales. Each department wanted a respectable bottom line figure for the dealer principal (Owner) to see on the monthly financial statement.

During those times, Ford would not authorize the dealer to replace a complete alternator, starter, distributor, etc., while under warranty unless it was burnt or damaged beyond repair. The only other exception was if the repair part(s) were code D99 which meant they were on backorder with no promise date. You still had to call the "Mothership" in Detroit to get authorization. And, you COULD count on getting a return call tag from the Warranty Center so they could have a "Look-See" at the defective part!
I kept Ford/Motorcraft stators, rectifiers, rotors, brush sets, bearings, and plenty of all the little widgets that seem to disappear between teardown and reassembly. The same for starters and distributors. The experienced Ford techs could usually tear down and replace the defective parts in a starter or alternator and have it back on the vehicle, while some of the newer techs were still trying to figure out what was wrong.
The only alternator I ever had a problem with was with a big case 70A version on my '72 429 Gran Torino. It didn't have power windows or rear defrost but still had that big hunk of metal hanging on the front of the engine. I had multiple problems with the brush holder and connector breaking. After several embarrassing breakdowns, I decided it was time for a fix. I hit the books and ordered a new wire harness, mount/adjustment arms, and hardware for a 65A alternator. One of the shop Techs had a like-new case, and with the previously mentioned alternator parts I stocked, he built a "new" 65A alternator for me and wouldn't charge me any labor. I was going to order a new one, but he said he could build one, and I would have a better alternator. He added that we took care of him, and he was paying it forward. And I believe I still have one of the 70A brush/holder-connector sets still lying around somewhere!
With increasingly stringent emissions laws and lots of new electronics, I guess you saw the 3, 4, and 6G alternators come on board with internal regulators and cooling fans during the mid-80s and 90s.
We sold quite a few of the 3G versions to people who owned 1st generation Mustangs that were daily/occasional drivers and not show cars. The 100A @idle and 130+A @ running speed, plus the ease of adapting it to your existing wiring with conversion wire kits, were welcomed by owners who had added electric cooling fans, megawatt stereo systems, and many other electronic gadgets that were now available. :)
 
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I agree 100% mrgmhale. The 70s and 80s were fun and great times. I met many interesting people, customers, shop personnel, and many from the Mother Ship (Ford Motor Company).
I had a great relationship with our shop techs. They knew they needed us to make a decent living. At the same time, even though I had fantastic retail and wholesale business accounts, I knew I needed them for good shop sales. Each department wanted a respectable bottom line figure for the dealer principal (Owner) to see on the monthly financial statement.

During those times, Ford would not authorize the dealer to replace a complete alternator, starter, distributor, etc., while under warranty unless it was burnt or damaged beyond repair. The only other exception was if the repair part(s) were code D99 which meant they were on backorder with no promise date. You still had to call the "Mothership" in Detroit to get authorization. And, you COULD count on getting a return call tag from the Warranty Center so they could have a "Look-See" at the defective part!
I kept Ford/Motorcraft stators, rectifiers, rotors, brush sets, bearings, and plenty of all the little widgets that seem to disappear between teardown and reassembly. The same for starters and distributors. The experienced Ford techs could usually tear down and replace the defective parts in a starter or alternator and have it back on the vehicle, while some of the newer techs were still trying to figure out what was wrong.
The only alternator I ever had a problem with was with a big case 70A version on my '72 429 Gran Torino. It didn't have power windows or rear defrost but still had that big hunk of metal hanging on the front of the engine. I had multiple problems with the brush holder and connector breaking. After several embarrassing breakdowns, I decided it was time for a fix. I hit the books and ordered a new wire harness, mount/adjustment arms, and hardware for a 65A alternator. One of the shop Techs had a like-new case, and with the previously mentioned alternator parts I stocked, he built a "new" 65A alternator for me and wouldn't charge me any labor. I was going to order a new one, but he said he could build one, and I would have a better alternator. He added that we took care of him, and he was paying it forward. And I believe I still have one of the 70A brush/holder-connector sets still lying around somewhere!
With increasingly stringent emissions laws and lots of new electronics, I guess you saw the 3, 4, and 6G alternators come on board with internal regulators and cooling fans during the mid-80s and 90s.
We sold quite a few of the 3G versions to people who owned 1st generation Mustangs that were daily/occasional drivers and not show cars. The 100A @idle and 130+A @ running speed, plus the ease of adapting it to your existing wiring with conversion wire kits, were welcomed by owners who had added electric cooling fans, megawatt stereo systems, and many other electronic gadgets that were now available. :)
I never had enough "spare" or old parts on hand to put together a complete alternator. For our Ford store, our factory rep was (also) fine with us rebuilding or repairing a failed starter or alternator, as he knew that is what we did with CP repairs, and were good at a proper diagnosis and doing repairs vs replacing parts. We were fine with the repairing approach as the larger part of the bill was for labor as opposed to minimal R&R labor and a high parts expense. While that could have been a good enough reason to repair vs replace (higher labor billing), that was at most a minor consideration - but it was a factor that left out Parts Manager a bit miffed. We had a Sun VAT-40 (I have one now also) which, like a Sun scope, in the right hands is a wonderful machines to use to diagnose battery, starting, and charging systems. No guessing at what was wrong once the VAT-40 was brought into the picture. No replacing the alternator and regulator in a shotgun repair effort.

In fairness the GPD (Genuine Parts Distributor) rebuilt units were a fairly high quality rebuild, and new components were also high quality. Our used car technician would use entire unit replacements vs rebuilding or internal component repairs, so I got a chance to see how good they were - and no kidding, at least the GPD parts we got in SoCal were really good quality.

In recent years, the one charging system issue I ran into was when I brought a 43 amp side terminal alternator to a local rebuild facility to install the higher capacity rotor for me, and rebuild the alternator (I no longer have the size soldering iron to properly handle the diode replacement, but I am going to get one for later use). The original alternator was working fine, putting out every bit of the 43 amps it was rated for. But, I had added dual electric fans, Classic Air air conditioning, GPS and rear backup & front view wireless cameras, installed a center console with a fabricated power outlet panel to recharge iPhones and iPad, installed a DashCam, etc. So, the 43 amp alternator was not able to keep up with the charging needs with all the goodies I had added. At 2,400 RPM it was able to put out 1 amp more than the total electrical draw with all electrical systems turned on (headlights, wiper motors, plus all the aforementioned items). But, at idle it just could not keep up with the electrical demand. But, with the upgrade the rebuild alternator did a great job - but not at first... After I installed it I initially had great power output, and all was well, but soon after the alternator was not providing the voltage and amperage needed. In fact, it has stopped working. I was surprised as the folks that rebuilt it have a really good reputation, and the tech who did the rebuild was well aware that I only came to him for lack of the soldering iron needed to do the diodes.

Long story short, when I removed the side terminal plug (and brush holder) for the Stator and Field circuits I saw the field circuit terminal was "missing." I initially thought the spade terminal had broken off. After pulling the alternator out I found the spade terminal had been pushed back into the brush holder, it had not been fully clipped into position, so it provided an intermittent open circuit, where sometimes the alternator provided output, other times it didn't. That was easy enough to fix, I had brought the unit back to the rebuilder, thinking I would need a new brush holder for the two spade terminals. But, all he did was pull the field terminal back out of the plug and put a drop of fast setting epoxy on it to make sure it did not get pushed back into the plastic holding block/brush holder again. That was good enough for me. He did put the unit on his bench tester, and we had good power from it. That was an unusual situation, something that I had never seen happen before, but I am glad I had at least been able to find the specific problem area as opposed to simply telling the rebuilder the alternator was "bad." It was an unusual enough situation that I actually did a YouTube video on the diagnostic steps, how the failed terminal holder situation was repaired, followed by testing the repaired alternator using the VAT-40. I have so much fun working on and tinkering with these first generation Mustangs and Shelby! Here is the YouTube video for curious persons who want to see more clearly what was going on in this one case:

 
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ok, so in the past I used to be able to use a pulley puller to remove the pulley from an alternator. I tried it on this alternator and destroyed the pulley and it still did not come off. I am a little disheartened It is a motocraft alternator. I am attaching a pick. Please tell me how to remove pulley.IMG_0373.jpeg
 
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I never had enough "spare" or old parts on hand to put together a complete alternator. For our Ford store, our factory rep was (also) fine with us rebuilding or repairing a failed starter or alternator, as he knew that is what we did with CP repairs, and were good at a proper diagnosis and doing repairs vs replacing parts. We were fine with the repairing approach as the larger part of the bill was for labor as opposed to minimal R&R labor and a high parts expense. While that could have been a good enough reason to repair vs replace (higher labor billing), that was at most a minor consideration - but it was a factor that left out Parts Manager a bit miffed. We had a Sun VAT-40 (I have one now also) which, like a Sun scope, in the right hands is a wonderful machines to use to diagnose battery, starting, and charging systems. No guessing at what was wrong once the VAT-40 was brought into the picture. No replacing the alternator and regulator in a shotgun repair effort.

In fairness the GPD (Genuine Parts Distributor) rebuilt units were a fairly high quality rebuild, and new components were also high quality. Our used car technician would use entire unit replacements vs rebuilding or internal component repairs, so I got a chance to see how good they were - and no kidding, at least the GPD parts we got in SoCal were really good quality.

In recent years, the one charging system issue I ran into was when I brought a 43 amp side terminal alternator to a local rebuild facility to install the higher capacity rotor for me, and rebuild the alternator (I no longer have the size soldering iron to properly handle the diode replacement, but I am going to get one for later use). The original alternator was working fine, putting out every bit of the 43 amps it was rated for. But, I had added dual electric fans, Classic Air air conditioning, GPS and rear backup & front view wireless cameras, installed a center console with a fabricated power outlet panel to recharge iPhones and iPad, installed a DashCam, etc. So, the 43 amp alternator was not able to keep up with the charging needs with all the goodies I had added. At 2,400 RPM it was able to put out 1 amp more than the total electrical draw with all electrical systems turned on (headlights, wiper motors, plus all the aforementioned items). But, at idle it just could not keep up with the electrical demand. But, with the upgrade the rebuild alternator did a great job - but not at first... After I installed it I initially had great power output, and all was well, but soon after the alternator was not providing the voltage and amperage needed. In fact, it has stopped working. I was surprised as the folks that rebuilt it have a really good reputation, and the tech who did the rebuild was well aware that I only came to him for lack of the soldering iron needed to do the diodes.

Long story short, when I removed the side terminal plug (and brush holder) for the Stator and Field circuits I saw the field circuit terminal was "missing." I initially thought the spade terminal had broken off. After pulling the alternator out I found the spade terminal had been pushed back into the brush holder, it had not been fully clipped into position, so it provided an intermittent open circuit, where sometimes the alternator provided output, other times it didn't. That was easy enough to fix, I had brought the unit back to the rebuilder, thinking I would need a new brush holder for the two spade terminals. But, all he did was pull the field terminal back out of the plug and put a drop of fast setting epoxy on it to make sure it did not get pushed back into the plastic holding block/brush holder again. That was good enough for me. He did put the unit on his bench tester, and we had good power from it. That was an unusual situation, something that I had never seen happen before, but I am glad I had at least been able to find the specific problem area as opposed to simply telling the rebuilder the alternator was "bad." It was an unusual enough situation that I actually did a YouTube video on the diagnostic steps, how the failed terminal holder situation was repaired, followed by testing the repaired alternator using the VAT-40. I have so much fun working on and tinkering with these first generation Mustangs and Shelby! Here is the YouTube video for curious persons who want to see more clearly what was going on in this one case:
Good afternoon mrgmhale,
Over a period of time, the techs’ spare parts stash accumulated to the point the Service manager would have to remind them to do some housecleaning around their stalls. If I had warranty parts Ford didn’t call for; I would donate them to the techs so they could salvage them for parts. I understand your Parts Managers position on techs not using their stocked assemblies vs using less profit-producing repair parts. As someone who stood in for the Service Manager for a few weeks while he was recovering from surgery, I see both sides of the fence. In parts, I wanted a better bottom line with more assembly sales. In the shop, there was more money to be made on labor repairing rather than the less profit producing replacing components.

State laws vary, but most did not allow for reman or used parts on a new car basic warranty. That and Ford’s requirement to repair rather than replace kept us from using any Ford Authorized Remanufactured (FAR) product. During the ’70s, the QC at each reman distributor varied widely, and the bad ones were well known by the Dealers. The Genuine Parts Distributor you mentioned and the Fred Jones organizations were much better than many on the QC of their products. That’s why Ford, who had dealt with customer and dealer complaints for years, finally had enough and revamped the whole process. The new program was Ford Quality Renewal (FQR). They took over the entire reman process, which gave them total control and consistency on the quality level of everything from window motors to engine/transmission assemblies. We finally had a trustworthy reman product and a decent nationwide warranty. (I believe the gas engine is 36 months, unlimited miles now).

Thanks for posting your video. The wire harness connector, brush holder assembly, and the blue wire on the stator blade were trouble spots for me. I had two other ’72 Gran Torino Sport Q-code cars equipped the same as the 429 car. They also had the big case 70A alternator, and I had the same trouble with the brush holder/connector on one of them. My M code Mach 1s are also similarly equipped with no power windows or rear defrost but had the small case 55A alternator. It must have been a thing the Torino engineers had with the big case alternator. I might add all three Torinos were equipped with the instrumentation group, which means they also had the amp gauge that was as useless as the ones in Mustangs. So no way to tell by looking at the instrument panel if the alternator was charging or taking a brief break!
As you posted, there must have been an intermittent open circuit that was testing my patience. I could check it in the shop, and it would be charging great. Let me go somewhere I wasn’t supposed to be, and you hear nothing but the familiar starter solenoid clicking sound we all know!
My parents had a 70A on their ’74 LTD and a 100A on a ’88 Taurus with no problems. So good chance my alternator just had it out for me! 😄
 

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