Battery light came on today on my drive home from work. 11.6VDC. Faint electrical smell from under the hood. I think it's coming from my upper alternator. I apologize for the brief story but I just spent 30 minutes crafting an entertaining story of my trouble today but my computer decided to shutdown before I could save/submit it.

Google-ing brings more questions than answers. Read of a 5A fuse under the hood (driver's side fender) for the voltage regulator. Is this it (What is This picture)? Here is my list of questions (take a deep breath):

1. Is there a delay before the charging system kicks in? Never payed attention but is there an amount of time I have to wait before I can expect the voltage regulator to up the voltage?

2. Also read of replacing the alternator doesn't fix the issue. Anything else I can check (fuses under the dash are good)? I can't find any fuse listed in my owner's manual that would be for the alternator/voltage regulator circuit. I also can't find anything about an underhood fuse box either.

3. Can I unplug the connector on my upper alternator without damaging anything?

4. Is it okay to run the truck at 11.6VDC (PCM, IDM, etc.)?

5. Are there good aftermarket alternators out there? I am not really interested in buying from Ford for about $400 for two (although they did last 14 years). I don't have time to get mine rewound so that is not an option at this point.

I'm looking for any way I can get back up and running tonight otherwise I'm driving to work tomorrow on my Optimas.

Pictures:
Lower Alternator - Reference point (looks okay)
Upper Alternator 1 - wide shot showing the blackened vents
Upper Alternator 2 - close-up of the upper alternator
What is This - is this the 5A fuse? A fuseable link maybe?

 

You can ruin your batteries running it with the alternator down. Yes, I have a cheap little meter in the cigar lighter and when you first start it shows a small delay until voltage comes up. I "think" it has to do with the glow plugs being on, then turning off. No, that is not the fuseable links.

Find your local auto electric shop and have them test it. Stores have a tendancy to say everything is bad. It is your most likely problem, as long as you do not allow it to kill a couple hundred in batteries. Your local shop can rebuild it for $60 or $70 and give you a warranty. Easy to pull!

http://www.justanswer.com/ford/5ubf0...ator-hood.html

Best of luck!

 

Not on our Trucks. Unlike more modern system designs which switch or reduce via the voltage regulator to conserve fuel. We have a Self-Exciting alternator is an alternator that has a special voltage regulator that doesn’t need an ignition wire to activate it.

What your referring to is found on 1999-2000 MY:

2003 MY has neither the fuse or under hood distribution panel

I am not understanding your question. Why would you wish to unplug the Alternator? The secondary alternator is dependent upon the primary for switching (on/off).

No, you will eventually stall. And place an undue strain on your Batteries creating yet another issue and expense.[/QUOTE]

Alternators are pretty straight forward. They're merely a Stator / Rotor. The primary issue is the Rectifier Bridge and Voltage regulator. Unfortunately, unless some one produces one I am not aware of, they are manufactured in both Mexico and China. "alternatorman.com" may sell one you can replace with a soldering iron. for a few dollars.

You can check for Voltage on either side. It should be the same. If not, you have found an issue that may be keeping your system from charging. But, not the Alternator itself.


Here are a few tests you can perform to determine what the issue is.

ALTERNATOR CHARGING:

Using a DVOM, connect the Red Lead to the (+) Post on the Alternator and the Black Lead to a known good ground. Record Reading. Reading should be 1 to 2 VDC higher than Battery System Voltage.

RIPPLE VONTAGE:

1. Ripple Voltage Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.

ALTERNATOR LEAKAGE TEST:

Alternator Leakage Current to check alternator diode leakage, connect the Multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.

 

Thanks for the info. I knew there was a change in 2002 with the new instrument cluster but didn't know if they updated some things or did a major revamp of the electrical system. Looks like the latter. While it crushes any dream of a quick/cheap fix, it does give me hope that I won't still be chasing this once I repair/replace the alternators. At least these bolt on and are a one person job. I don't miss the 70's and 80's trying to tighten down the adjustment bolt while my dad was using a crowbar to hold tension on the belt (yes, I'm old).

My alternator(s) have one large cable coming out of it (4-6 gauge maybe) and a plug with two wires. I'm assuming that the cable coming out is the (+) post. Is there a place to get good contact or am I going to have to pierce the sheath? I would prefer to not do that if possible.

I tried to look up Ford alternators on-line and there were lots of options (none of which were 110A) so I went by the dealership to find out the part numbers. They told me that they were the exact same alternator and both have a voltage regulator that operates independently so that either alternator could be "unplugged" and the other would carry the load. Looking at the alternators I knew that wasn't true since the connection orientation is not the same. I wasn't sure about the voltage regulator(s) since this is my first dual alternator setup and I've not had any problems with it until now.

Unfortunately I am being audited at work this week so I do not have the option of coming in late or taking a personal day to figure this out. This couldn't have been timed any worse.

Thanks for the early post.

 

You don't have to remove any insulation. The Cap is rubber (if its still there) and can be lifted away for testing.

 

So I've mooched a loaner vehicle for a couple of days to figure this out. I called three well-reviewed electrical shops and got these answers:

1. Shop #1 said it would be about $85 to rebuild each alternator (drove by the shop on the way home from work and it is NOT somewhere I would have considered stopping at if I hadn't seen some good on-line reviews).
2. Shop #2 said it would be about $250 to rebuild each alternator (because they are "heavy duty").
3. Shop #3 said that nobody really does that any more and that they just order them to install (he never called me back with a quote so I don't know how much it would cost to order through him).

Not very promising with that many different answers. If I'm going to spend $200 for an alternator I might as well get an upgrade. Has anyone dealt with or know anyone who has used one of these:

https://alternatorparts.com/6g-serie...lternator.html
High Amp Ford 3G, 4G & 6G Alternators, 200-300 amp Ford Alternators, Nations Starter & Alternator

I also looked at http://www.partsgeek.com/catalog/200...lternator.html. They sell A/C Delco, Bosch, Denso (OEM manufacturer?), Remy, and Pure Energy. They offer new and remanufactured. Any good/bad on any of those? I picked this one in particular because they actually show upper/lower alternator options. While they are the same alternator the rear of the case is offset on the lower alternator compared to the upper. I don't know if this is something I can just unbolt the back of the alternator and rotate or if it needs to be assembled in the correct orientation.

They say the large case fits but does it REALLY fit? I've seen more than my share of "direct replacement" claims that require trimming/grinding. I'm sure that the bolts line up and the plugs are the same but does the larger case fit without modification?

 

I would take them to number 1 and have them test them. They will do that for free. Sounds like our shop here. Run by an old biker. Nicest guy in the world.
Turned out to be a good friend.

 

Danger Will Robinson, LOL.

Had a bit of a smell, funky voltage, chased it for a while until CHRISTMAS NIGHT and wouldn't start or charge. Limped home for quite a while

It could leave you walking

Here's the alternator I used as a higher amp replacement. I did grind the mount a bit, but then used washers as shims later. Gave me a little bit more clearance from the "dual alternator upper radiator hose"

https://www.ford-trucks.com/forums/1...l#post15897048

If it is starting to go, get it replaced quickly.

 

That's what I'm doing now. I had to drive it the other day as I don't live near any co-workers and I had to be at the office. The charging system worked for about 1/2 that drive and I was at 12.6 volts giving my batteries a little bit of a break (my batteries definitely did not like going to work with the headlights on and no charging for the first leg). Luckily my dad doesn't need his work truck this week so I've got his Chevy to commute in while I wait for my alternators. I can tell you truck brand loyalty is alive and well in San Diego as the looks I get driving my dad's 2006 Duramax are a lot different than the looks I get driving mine.

I went with the HD 140A single rectificer/bridge 6G from alternatorparts.com. I'll probably have my originals rebuilt at a local shop and keep them as backup.

With such a close fit to the upper radiator hose (as ExPACamper talked about) my plan is to grind a bit and minimally shim the upper alternator for hose clearance and grind the lower bracket to flush mount that alternator. I'm sure it's a nominal change in pulley position but I'd like to minimize any additional stress on the belt and tensioner.

 

A follow-up to close out my issue...it's finally fixed! The alternators were bad (at least the upper one was). From what I understand the upper is the primary and the lower is the slave (electrically). I wasn't going to replace only one as putting new with old makes new older quicker (similar to batteries). I contemplated going single alternator but I didn't know how the wiring was set up and if that would cause a problem. This would also leave my signal plug and a main line exposed on the underside of the engine (no matter how I insulated and secured them) and that was not an enticing idea either. After some investigation, contemplation, discussion, and buck$zooka confirmation I reached a decision. I opted to upgrade to a new alternator with a larger case. Both of my alternators were the 6G style and I ended up getting these:

8253M-HD140 - High Output Alternator, 6G, 140 Amps, Power Stroke and Ford Diesel, Heavy Duty, Large Case

The lower alternator is clocked differently (the back side plug and terminal are rotated differently compared to the case).

The job was not that hard...sort of. The upper alternator was comparatively a cinch (obviously disconnect both batteries first):

1. Pop the belt off
2. Unplug the alternator
3. Remove the main line (10mm socket)
4. Remove 3 bolts (13mm)
4. Bob's your uncle

I had to do some grinding on the bracket to turn the arch indo a deep 'V' to accommodate the larger case (the bracket has a 'U' shape from one side to the other). The new alternator was shipped with washers for spacers to raise up the unit to clear the bracket with no (or minimal) modifications. I wanted an air gap so I ground the bracket down for clearance with no washers. The larger case sits VERY close to the upper radiator hose (if you have the around-the-alternator hose) so I chose to put two washers at each mount (about 1/8" total) to give it a little extra breathing room. I also had to drill out the terminal lug slightly as the terminal on the new alternator was a tad larger in diameter. All said and done total time invested in the upper alternator was about 45 minutes.

The lower alternator was a completely different beast that I was not ready for. The only way to get to it was through the wheel well. That meant removing the liner. Definitely some finesse to that unless you don't mind chipping the paint on the quarter panel. Same removal process as the upper alternator except not much room to work with. I used ratchet extensions and a universal in there to reach the bolts. After 14 years of underhood temperatures it definitely takes more than 35 ft-lbs to break them loose (thought I was going to snap one of them I was twisting so hard). In hindsight I should have sprayed some PB Blaster on them but it never crossed my mind since they were 'just alternator bolts'. After feeding the alternator out above the frame rail I realized there was absolutely no room to get a grinder in there to turn the 'U' to a 'V' in the bracket. Easy enough...NOT. After removing the tensioner I found two of the bolts to remove. Not the most convenient locations but at least reachable (even if it was only 1/4 turn at a time). The last one took me some time to find. There's a nut holding the transmission fluid line bracket onto a stud...or is it? It's the third bolt! I used an exclamation point because it took me a couple of hours to figure that one out (don't judge me, you weren't there). It's just like the forward bolt on the passenger's side valve cover that doubles as the bracket for the oil dipstick tube. The bracket also comes out through the well also. Luckily the brackets are aluminum and grind easily. There were no clearance issues (after grinding) so I did not use any washers to re-install. Re-assembly is in the reverse order. It was a tight fit to get the larger case into the engine bay and positioned.

The new alternators came with a bolt on the rear of the case (OEM comes with just the threaded hole) for an alternate ground to the battery. I went to Pep Boys and got two of these:

https://www.pepboys.com/product/details/9405770/01454

There were a few extra inches on the passenger side when I was done (the driver's side was just about right) but the next lower size was 40" long and I don't think that would have made it based on the routing I used (along the negative cable to the battery on the passenger's side). Total time actually invested into the lower alternator was along the lines of 4-5 hours based on getting my butt kicked by the lower bracket and the interference R&R.

These times are all estimated for labor to get the job done with all parts on hand. The alternators took a few days to decide on and another week to get after I ordered them. Toss in the fact that my dad loaned me a truck and it took me four weeks to accomplish. It's amazing how repair time is not a priority when you have a means of transportation. If I was borrowing my wife's vehicle during this time she would have kicked me to the garage the moment those alternators arrrive it would have been done in one day (minus the week to get the alternators).

 

Brian42... nice write up. Reps headed your way. (Whoops... it appears as if I've already repped you for something else too recently).


Questions:

1. On the lower alternator install, using the larger 6G case, you removed the bottom cast bracket to grind a bit of clearance. Was the clearance necessary for the larger circumference of the bigger 6G alternator? Or was the clearance only required for the alternator case bolt protrusion that ends up in the center of the valley of the bracket?

2. How much room remained between the larger lower alternator and the boxed passenger frame rail in the near vicinity?

3. Did alternatorman's 8253M large case 6G alternators ship with pulleys installed? If so, did both alternators ship with the SAME size pulley's, or different size? (ie, the OE lower pulley is 5mm larger in diameter than the OE upper pulley, on purpose to create a different drive ratio between the two alternators, which would effect turn on excitation based on rpm). Or did you swap your original pulleys from your old alternators?

4. The larger case alternators have a rotating axis that is spaced further away (than the small case alts) from the imaginary reference plane defined by the mounting bolt lands on the alternator brackets. Any change in location of the rotating axis of accessories driven by the belt could effect the range of tolerance / amplitude of movement afforded by the automatic belt tensioner as the belt stretches and contracts with temperature. Shifting the rotating axis of one alternator further out (or up, in the case of the top alternator) would likely fall well within the tolerance range of the tensioner. But you changed TWO alternators to larger diameter units, and furthermore added a couple of washers to each bolt on the top alt to clear the rad hose better. I am curious about the cumulative "stacking of tolerances" that the combination of two larger diameter accessories present to the FEAD system, in terms of reducing the range of belt tensioner movement, necessitating a slightly longer belt to restore optimal operation?

Using slightly smaller pulleys than the original pulleys on the old small case alternators could solve the need for a longer belt, but create a new problem with operating an alternator outside of it's max rpm range under pedal to the medal acceleration. And finding the right IDxODxWD pulleys with the correct A distance between the DRE and the first groove for proper belt alignment is a trick that is probably more difficult than finding a longer belt for this application, especially when the dual alternator with air conditioning models already have the longest belt Ford specified. And, the pulleys still need to be a different size, so that the alternators don't fight with each other. There is a question or two in these last two paragraphs somewhere, but the exact question largely depends on what pulleys and belt you ended up using, and what thoughts you gave to the subject of belt tension amplitude... so I'm curious what your thoughts and solutions were.


5. Did you have any issues with the lower alternator pulley not aligning with the rest of the FEAD (front engine accessory drive) system?

 

It was for the case bolt as far as I can tell. I cut a little extra out of the bracket to add a little extra air gap for flow and cooling.

I'd say about an inch or so gap between the frame and new case.

They both came with the same size pulley I think (not something I was checking for but they seem to have the same as the OEM ones and were about the same size). They came with everything installed and were grind, plug and play. I opted to hook up an alternate ground so picked up two extra cables.

From my understanding of what I've learned through the process is that the alternators work together and that the upper alternator is the primary (the lower is considered the 'slave').

I had the same concerns about increasing the distance the belt will need to travel. The case is basically a swollen small case so the center point seems to be the same (hence the need to carve out a little extra flesh from the bracket). I went back and forth about adding the washers ('spacers') to the brackets in fear that I would stretch the belt and put a strain on the tensioner, which in turn would accelerate belt wear. I already have a long enough list of alternate required parts due to modifications and repairs and having to order a custom belt is not something I was interested in adding. I did not need to add any spacers on the lower alternator since there was nothing routed nearby it so the only decision I had was to add to the upper or not. I approached it with idea of not adding any washers until I test fitted it after grinding. It left very little air gap between the case and hose (I have the hose that routes AROUND the belt). I decided to add the supplied washers to the mount (2 washers which is about 1/8?) to gain a little extra clearance (about 3/8" clearance between the hose and case). After putting the belt back on the tensioner is pretty much in the same place as before and I haven't had any issues. If it becomes a problem or my belt seems to wear out faster I might re-visit the issue but I'll see how it goes. My only real recourse would be to remove the washers and either live with the smaller gap or get the single alternator hose that goes through the belt (neither of which seem very appealing options).

Not at all. Everything lined up fine. Holding both alternators side by side it looks like everything is in the same location but with a bigger case. After I finally figured out how to get the lower bracket off things went smoother after that. The brackets are aluminum so grind easily (and the oxide layer they form is better protection than most anything I could have bought to coat them with). There's not a lot of room to work with for the lower alternator so it is time consuming to put the puzzle back together but it all lined up fine (eventually) in the end.

Now you've got me curious about the pulley sizes. I'm going to have to measure the pulley sizes over the next couple of days (I still have the originals sitting my garage) and see what's what. Just when I thought it was safe to move on to the next project...

 

In our vintage trucks, the alternators are not PCM controlled in the modern sense of the term. As such, the only way the lower alternator can be considered a "slave" to the upper alternator in normal operation is if the pulley diameters are different, like the factory set up the pulley diameters to be. Pulleys are what determine the drive ratios, and therefore the current producing curve, of our internally regulated alternators, which function independently, and are self controlled.

Ford specs the upper (top) alternator pulley ratio at 2.49:1, which in the case (ha ha) of the OEM small 6G, calls for a 64mm diameter pulley. Ford specs the lower (bottom) alternator pulley ratio at 2.32:1, which calls for a 69mm pulley. As you can see, the lower alternator pulley is 5mm larger in diameter than the upper alternator pulley. This makes the upper alternator dominant, because for every RPM the engine turns, the upper alternator will turn faster than the lower alternator. I'm sure you've heard of car stereo enthusiasts putting smaller pulleys on their alternators to make them spin faster and produce more current at lower engine RPM. Essentially this is what Ford has done, relative to the lower alternator, making the upper alternator "dominant."

The faster turning of the upper alternator will cause it to be first to generate power, because a self exciting alternator has a minimum RPM threshold that needs to be met in order to "turn on", so to speak. This is often illustrated in alternator output graphs. In the case of the upper alternator, each alternator RPM would be divided by 2.49 to yield the engine rpm required to reach any point along the line of the alternator graph. Likewise, the lower alternator rpm, using the same output graph, since both the alternators are identically rated, would need to be divided by 2.32:1 to see what the engine RPM would be at any point on the output graph.

When you think about it... the original alternators were exactly the same, top and bottom, other than the output post riser and the rectifier clocking (position, not timing). These two external differences effect only the plug position on the back. The changes have no effect on alternator output, because the rotors, stators, rectifiers, diodes, brushes, regulator, and slip rings are all identical to each other. Therefore, how else can one of these identical alternators be "primary", or "slave", to the other? The only way is by altering the drive ratio, which is exactly what Ford did with the different pulley sizes.

Your large case replacement alternators are identical to each other also. Therefore, the only way to replicate Ford's engineering intent of one alternator being primary and one being secondary is through differential drive ratios... accomplished by dissimilar diameter pulleys.

There is only one instance where the PCM actually "controls" our vintage of dual alternator systems. And that instance is only 120 seconds in duration, when the glow plugs are commanded on. When the PCM sees the glow plugs are ON, the PCM interrupts the "I" circuit to the lower alternator only, and only for the 2 minute max duration that the glow plugs might be on for. That's it. The PCM monitors the output of the alternators in order to report trouble codes if the output is low or non existent, but otherwise exerts no other control over the alternators. It simply stops the voltage regulator in the lower alternator from seeing the lamp circuit until the glow plugs time out.

This is somewhat counter intuitive, since the glow plugs can draw well over 100 amps, and combined with cranking the starter at another couple hundred amps, not to mention the batteries discharging overnight and hungry for some current. One would think that cold start mornings is actually when we would want to see both alternators producing power, not one completely blocked. But Ford's rumored reasoning is that if too much current is available when the glow plugs are on, the glow plugs will end up cooking prematurely. The emissions regulators want to see those glow plugs working at all times required to reduce cold start emissions, so the glow plug survival took priority.

 

Plus if the drive ratios were identical I would expect they'd frequently come on and off in synch, putting unnecessary peak loads on the system. With different drive ratios the peak loads will spread out. Maybe even alternate.

Got a reference to pin down the amp draw? I was trying to spec out a solid state relay to replace the GPR. They get pricey at those amps.

Reps to both of you for a great thread!

 

My new alternators both have the same pulley. Measuring the diameter on the front of the pulley (lip to lip) my OEM upper is 66mm and lower is 70mm. The pulley on my new alternators are 60mm each.

I called the shop that I bought them from and asked about the underdrive and he said I can do it if I want to but there's no need.

Next I consulted Google and was not able to find out any concrete engineering explanation for the underdrive on the lower alternator.

Feeling that there was a sound electrical reason for this design and agreeing with Y2KW57 and aawlberninf350 that there might be something detrimental (similar to crossing the streams in Ghostbusters...total protonic reversal!), I called three local electrical repair/rebuild shops to consult their wisdom. They all said it doesn't matter if you underdrive one of them or not.

I feel I have gathered enough evidence to alleviate my concerns (although I am still not completely convinced...there must be some reason for the underdrive). Unless I can find some compelling evidence that I'm charging my batteries too fast or creating a riff in the time-space continuum, I plan to leave things as is.

If I am wrong, please feel free to correct me and prevent me from blowing up my truck and those around me.