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Do the experts agree with this conclusion? What I plan to do with mine if all agree.
Charlie



I'm not an expert, and I don't agree with the OP's conclusion.


First, the OP said he cut his fusible links. I would have never done that. Fusible links perform differently than fuses. Even though one can obtain high current Maxi fuses and ANL fuses that have the same ampacity as several paralleled fusible links, the types of circuits and loads where an OEM still installs fusible links to this day, despite the availability of other high capacity current limiting protection devices, should be noted. Typically, OEMs use fusible links in the starter and alternator circuits. Clearly, the OEMs must still have a good reason for doing so.


One reason that comes to mind is inrush current spikes. When the key is turned to start, as much as 2,500 amps of current can transiently pulse through the cables that feed power to the starter. That pulse cranking current is very brief in duration... instantaneous... but it is certainly enough to pop a fuse. A fusible link can tolerate a longer duration of high amperage transients, which eliminates nuisance fuse pops, and yet still provides protection against dead shorts.



The same holds true in alternator circuits that recharge the batteries. After being depleted from glow plug operation and cranking, the batteries are primed to accept up to 500 amps inrush current once the alternator is kicked on by the engine. Sure, the alternator may not be able to generate 500 amps, but depleted batteries will take all the current the alternator is capable of producing, which maximizes the current flowing through the wires protected by the fusible link. If those wires are protected by a fuse instead, then a higher rated fuse might be needed to prevent nuisance pops, and the higher rated fuse reduces the protection margin of error for the wire being protected.


More than anything, fuses and fusible links are sized for the WIRE from the power source servicing the equipment. Fuses and fusible links are not sized to protect the equipment itself... especially on high current circuits (as opposed to computer module circuits). So the gauge size and number of parallel fusible links, or the amp rating of the fuse selected, must be indexed to the wire being protected, not the load expected. If more load is expected, then the wire size must be increased, and then commensurately, the fusible link or fuses are then increased to match the higher current carrying capacity of the bigger wire.


The second thing the OP said in his conclusion is that the two 12 gauge fusible links were protecting an 8 gauge wire. This doesn't make sense to me, because a fusible link is typically 4 gauge sizes smaller than the wire being protected. So while a single 12 gauge wire is indeed appropriate for protecting a single 8 gauge wire, TWO 12 gauge wires would NOT protect a single 8 gauge wire. Furthermore, the factory alternator B+ cable is 4 gauge, not 8 gauge. Now, a 4 gauge cable can by appropriately protected by two parallel 12 gauge wires. I suspect that this is what the OP meant, but his conclusion does not say this, and therefore his conclusion cannot be agreed with.


Thirdly, the OP has selected a 150 amp rated fuse for his 4 gauge wire, a wire which his research found was rated up to 160 amps (assuming a distance of less than the width of the engine bay). Even while the 150 amp fuse is less than the 160 amp wire, the difference is still not enough to meet the minimum 15% derating of the wire, due to it being in the engine compartment exposed to high ambient temperatures. To meet that criteria, a 136 amp fuse, or the nearest down rated fuse, which is 125 amp, would have needed to be selected. And yet a 125 amp fuse might be more vulnerable to nuisance pops... which reminds us why OEMs use those short lengths of skinnier wires instead... aka fusible links.


It isn't just the smaller diameter of the wire that makes fusible links... it is the characteristics of the insulation... which is rated to have the wire inside burn up and separate within the insulation, without burning the insulation itself in the process, which could create a flame and source of ignition in the engine bay.


I upgraded my alternator to a 230 amp rated beast. I left all the factory wiring in place, untouched, as is, with fusible links intact. To handle the additional output of the alternator, I added two additional 2 gauge cables, one directly to the positive post of each battery, with the other ends stacked on to the B+ terminal of the new alternator. I protected each of those two new battery charging wires with a relatively recently designed (within last 10 years) Buss Marine Rated Battery Fuse. What I was after in upgrading my alternator was better battery charging, at lower rpm (idle). It has provided that. My current batteries are now in their 10th year of service, with no sign of weakness. I noticed an improvement in the residual charge of the batteries after the alternator and battery cable upgrade.
 

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I did the same as NYB....changed NOTHING ......220 amp ALT ......did not add wires or anything .....( In my Van ) ...I did not touch the charging wires.... I am in my 6 th year ....don't believe all the Misinformation....
 

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I did the same as NYB....changed NOTHING ......220 amp ALT ......did not add wires or anything .....( In my Van ) ...I did not touch the charging wires.... I am in my 6 th year ....don't believe all the Misinformation....



Just so that it is clear, I did not change any of the existing factory wiring, but I did add two fused charging cables from the B+ output stud on the high amp (230a) alternator directly to each battery.


The factory wiring would be overtaxed otherwise, leading to increased risk of wire overheating and subsequent wire fatigue. Providing an alternate path for the current to flow to the batteries... a new path that has less resistance than the factory charging wire... distributes the heat and current load borne solely by the factory wiring alone to an additional conductor(s), and thereby reduces the risk of original wiring burn outs.


Low resistance battery charging cables enable the batteries to obtain the output current of the alternator more efficiently... meaning that the batteries can top up faster, and maintain a higher overall state of charge, which reduces the depth of discharge that impinges on long term battery life.


So while I recommend leaving the factory wiring alone, I also recommend the installation of additional charging cables to share the current load for replenishing the batteries, which alleviates the load and the heat from the factory wiring that was not sized to handle the higher output alternator.


The foregoing secondary recommendation is not based on internet forum fueled "misinformation." The guidelines for upgrading the size of alternator B+ wiring when a higher amp alternator is retrofitted were written and recommended by Ford Motor Company, in the instructions for the higher amp alternator I used, which was a Ford OEM part.
 

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Using the old wiring, alone, not recommended by Ford or Leece-Neville.
The old wiring has too much resistance to larger current flows, gets hot.

http://elreg.com/wp-content/uploads/pdfs/AVI160T2002-3 Install Procedure.pdf


bulletin_q_67_5f34642a8e319aa1abfcdc3096a112858a699a4e


Frank, you have some very interesting photos in your Flickr Photostream, including one of my photos, that you posted in your quote above.


No worries... I don't mind you hosting it or posting it, as the content was originally created by Ford, and I only added the red line to the text for emphasis.


But I had to mention that I originally made the photo of this bulletin, and added the red line, and uploaded it to the internet where you found it...for a reason. And that reason is to help other readers of this thread understand that you are using this photo and it's emphasis out of context in this thread, because what we are talking about here is upgrading the wiring to accommodate the higher current generating capacity of an upgraded alternator, and what the photo and its red lined emphasis is talking about is to strongly discourage upgrading the alternator altogether, regardless of whether or not the wiring is upgraded or supplemented.


The risk that QVM Bulletin 67 is identifying for 7.3L owners relates to the limited current capacity of the glow plugs. Unlike the Beru three stage GN series glow plugs Ford used in the 6.0L and later diesel engines, the glow plugs in the 7.3L diesel are the older Beru two stage GV series glow plugs, which were designed by Beru to only operate as pre heaters prior to start, and during start. As a presumably low cost way to quickly comply with cold start emissions standards initiated in California, Ford decided to program the PCM to permit these two stage glow plugs to operate as three stage cylinder heaters. The third stage is the amount of time the glow plugs remain on AFTER the engine has been started (when the alternator is turning and producing current).


This third after start stage of glow plug operation continues long after the Wait To Start (WTS) indicator light on the instrument cluster goes out. That little dashboard light is only on for between 7 to 10 seconds, whereas the glow plugs themselves can and will remain powered on for up to 180 seconds after start, depending on engine oil temperature. The purpose of the glow plugs remaining on even after the engine is already successfully running is to reduce NOX emissions which occur at colder combustion temperatures. By artificially heating the combustion chamber for up to 3 minutes after start, NOX levels are reduced.


The problem is, our glow plugs are not designed to run at 12 volts. They are actually rated to operate at 11 volts. During cylinder pre heat, prior to start, and during start/crank, but prior to run, the system voltage is generally around 10 volts, since all that pre heating current and starting current is being supplied by the batteries alone, without the aid of the alternator, because the engine isn't running yet. But once the engine is running, and the alternator is turning, the system voltage increases, up to the limit of the voltage regulator, tempered by the current demand to replenish the batteries, and the current generating capacity of the alternator at IDLE.


Ford's OEM 110A alternator's current generating capacity at idle is only 50 amps. If the batteries are depleted from supplying 80 to 125 amps of current to the glow plugs, plus the 2,500 amp transient and momentary amp load in the hundreds for starting, the battery demand for replenishment will by high, and the OEM alternator will not be capable, at only 50 amps of generation, of producing enough current to bring the system voltage significantly higher than 12 volts for the first minute or two of engine operation. We can literally hear the subtle transition in the idle speed, as well as monitor the voltage with a gauge or on board monitor, when the load from the glow plugs ceases and the OEM alternator catches up to the ravenous battery charging demand. Then we see voltage normalize to the setting of the regulator, at 14.4 volts (typically measured .20 less in cab due to a diode protecting the PCM, so 14.2v).


The point? The point is, Ford is RELYING on ANEMIC alternator performance in order to PRESERVE the service life of the GLOW PLUGS. That is why I made that photo above of QVM Bulletin 67, and that is why I put that red line to underscore one sentence... to emphasize that Ford does not want us to "upgrade" our alternators period, no matter how much more copper we drape between the alternator and the batteries. Even where Ford outfitted the 7.3L with two alternators, Ford programmed the PCM to shut the second alternator off anytime the glow plugs are on. This was to maintain anemic alternator performance, or lower system voltage, during the third stage of glow plug operation (after start), using glow plugs that are only rated for two stage operation (pre start and during start).


Notwithstanding, I upgraded my alternator. I defied Ford's instructions for my vehicle application, even while I followed Ford's instructions for installing (and upgrading the vehicle wiring to accommodate) the larger Ford alternator (yes, made by Leece Neville) that I installed. The potential negative consequences of my decision are entirely predictable. My glow plugs might fail prematurely, due to the fact that my alternator can supply 100 amps of current just off idle (double that of the 110amp alternator). The peak rated capacity is not of concern for comparison's sake, because by the time the engine is operating at peak rpm for maximum rated alternator performance, the glow plugs are already off.


So, alternator upgrader beware: by upgrading the alternator, the glow plugs in the 7.3L are more vulnerable. The physical dimensions of Beru's (OEM for Motorcraft Glow Plugs) later three stage designs (ie ZD-12, -13, and beyond) will not fit our 7.3L. We are stuck with ZD-11's, which are two stage glow plugs that are rated to run on batteries alone, and not designed to tolerate the full scale output of a robust alternator, since the improvement in the power generation capability that is capable of increasing the system voltage will commensurately increase the current according to Ohm's Law. And that ends up pushing our glow plugs beyond what they are rated for.


Which is the reason why I uploaded the red annotated photo to the website you copied it from, and is the reason why Ford saddled us with such a sorry performing alternator in the first place. This post was not intended to explain electrical theory, as I suspect that you have forgotten more than I will ever know, given the number of radios and other electrical equipment presented in your photo stream. The purpose of this post is simply to explain the context of my underlined emphasis, which identifies a risk to the glow plugs that anyone who is considering upgrading their alternator should consider, if they have a 7.3L Super Duty that they are working with.
 

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Wow, NYB...are you well verse'd in this this!

I just learned a ton of info from your post and now understand better, why my truck does what it does from a charging prospective so thank you for that.

I upgraded by alternator and wiring as per my work log below and even with the 220A alternator, I see my headlights cycling bright/dim and watch my voltage move up and down for the first couple minutes of driving if I start the truck, turn on the lights and head out immediately. My only concern that came to mind is how does it affect the FICM. I guess I need to watch the FICM PID's to see what they are doing.
 
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