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But I had to mention that I originally made the photo of this bulletin, and added the red line, and uploaded it to the internet where you found it...for a reason.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.