The GP differences are known.

The more I'm reading the less I'm worried about the GPs, I just don't care for the fluctuations. I believe the GPCM is a Beru unit, and while the manual describes voltage as being one of the deciding parameters, it very well could be the GPCM that is shutting down at 14.4v, my read from the videos.

The current flow acts as though these may be the self regulating GPs.

 

Yes, they are self regulating GPs.

But the heating coil itself isn't. Even in your fancier GN series (mine are the older GV series), Beru still describes the heating coil as having an electrical resistance that is "effectively independent of the temperature."

So the part that pokes into the cylinder and does the work (and does the damage to the cylinder when it overheats and breaks off) has more or less a fixed resistance.

From Ohm's law, if the resistance is more or less fixed, and we increase the voltage, then we commensurately increase the current that heating coil will have to deal with.

Yet, that heating coil isn't the only resistor inside the glow plug. There is also a regulating coil that has a very high temperature coefficient, making it very responsive to increases in temperature, and which acts as a variable resistor. As long as that regulating coil heats up fast enough, the resistance will increase and the current will decrease, even if we slightly increase the voltage with a higher wattage alternator.

But Beru describes a problem that can crop up if and when this regulating coil is somehow "blocked" from seeing the total rise in temperature. A very small annular ring that surrounds the pencil body of the glow plug, and this ring gap is how the regulating coil gets access to "feel" the developing heat in the cylinder, which further increases the resistance of the regulating coil in order lower the current sent to the heating coil. If that annular ring gets coked with soot, then to that extent, the glow plug's self regulating coil is blocked from seeing the heat. (The regulating coil will still see the heat back fed from the heating coil it is feeding, however.)

The foregoing is a scenario that Beru describes. I share it here in this discussion on alternators as a counterpoint to my own desire to hear from folks who've upgraded to high amp alternators... and how long their glow plugs lasted in the years following. Well, some folks who are inclined to modify one aspect of their vehicle, tend to modify other aspects, including deleting and running a chip. If their program of choice over fuels and creates black smoke on heavy throttle, would their sooty burn contribute to blocking the narrow ring gap in the glow plug that Beru describes as contributing to the regulating coil's ability to see temperature? Then why did their glow plugs fail... because of the alternator, or because of the chip? It would be very unlikely for them to know, because it could very well have been something else too. So my asking users is kind of non productive.

Getting back to I=V/R, a high amp alternator, and a fixed resistance heating coil that depends on an impacted regulating coil and an anticipated range of supply voltage, I found it interesting to read that the nominally rated operating voltage of the ZD-12/13 is 11v. Key on, engine off, it is normally seeing 10.5v to 12.5v.

Fortunately, at 32 degrees F, the heating coil in the 6.0L glow plugs can reach 1,832 degrees F within the first 2 seconds, because the heating rod tip was narrowed to make it heat up faster. The faster the glow plug can reach ignition temperature and continue to heat up the cylinder during the WTS light period BEFORE turning the key, the less time the glow plugs need to be on after the engine is running and the high amp alternator is cranking out high voltage. At 23 degrees F, it takes 5 seconds. At 20 degrees F, 7 seconds. The increase in time isn't linear for every degree it gets colder, so as it gets down in the teens and below zero, the glow plug's exposure to prolonged on time at higher alternator voltage increases. Beru claims reliable starts down to -22 degrees F, unassisted. But that might mean a full three minute burn.

I don't have 180 second capable on time glow plugs, but 6.0l folks do. What comes with the 180 second glow plugs is supposedly a capability to withstand a system voltage of 14.5v. Yet, I still find that the concerns I have about the L-N 230A alternator providing too much voltage for my glow plugs to be real, and founded in this paraphrased statement from Beru... which basically says that the style of glow plug I have would be damaged in a very short period of time if I ran it in a 6.0 (pretending for the sake of this discussion that the fitment were exactly the same).

So, I'm going to end my sharing of this informal investigation on this particular subforum, because it now becomes clearer through this research that 6.0L owners are less vulnerable to this concern. Even though the window of potential glow plug operation after engine start and while the alternator is running is 50% longer in the 6.0L application than the 120 seconds of the previous model, apparently your glow plugs are set up for it, where mine are not.


Finally, here is a parting shot of a Ford diesel truck relay dating back to the days of IDI, early 90's vintage, pre "Powerstroke". The big wavy nichrome like resistor, that looks not unlike a smaller version of the same type of load resistor found in a professional alternator and battery load tester, is on the output side of this glow plug relay. When the relay is energized, battery voltage must first work it's way through the pre calibrated resistance of this metal wave before it can reach the glow plug controller circuit board in the black box below. This isn't like the bank dividing shunt that Ford used a few years later in California trucks for diagnosing which bank of glow plugs has a fault... no, this wavy thing is a true resistor. The stock glow plugs that accompanied this controller are about half the length of the current self regulating glow plugs. I assume that the earlier glow plugs didn't have their own built in regulating coil, and this big resistor served to step down vehicle power to something the glow plugs could tolerate.

 

I agree if I still had the 7.3L my worry would continue.

The bottom line for a 6.0L owner being

A tech resource for glow plugs from F-M:

http://beru.federalmogul.com/sites/d...gb_2014_fm.pdf

But I didn't find any direct info about our GPCM.

So my takeaway is between the glow plugs themselves and the GPCM we are protected as best we can be, but the fact that the glow plug circuit is designed to shut down over 14.4v and some of the alternators can output 14.5v during initial cold running can get us into a situation of erratic control.

I had a Monday morning response from L-N that they were scratching their collective heads over this, and hopefully more to come.

 

At least you heard back from L-N. I haven't heard back from Beru yet. Some information in my post above was derived from two Beru documents that I assume are similar to the one you linked from F-M (because I could never get the one from F-M to download!)


I also had difficulty finding more information about the GPCM. I thought to try using the Beru part number "0 521 151 001" which crosses to a Navistar 1828565C1. If the Beru part number on the GPCM that you removed from your truck is different than 0 521 151 001, then that might be an interesting Beru number to search.

 

It would be interesting to let the glow plugs time out and then start up to see what happens, just a thought.

 

Somewhere else Jack pointed out that the fuel pump also has a time-out on it. It is very possible for that time-out to occur prior to GPM time-out, which means you are running your injectors initially off static line pressure - not a good thing.

I've changed my start procedure since learning that pearl of wisdom: WTS light goes out and I crank 'er over...

 

That's pretty much the way I have always started my PSD back to my 97 f-350

 

After reading the Beru/Federal-Mogul information, there should never be any reason to double hit the Wait-To-Start function, it just runs down the batteries more.

 

The fuel pump should be running when the WTS light goes out... never wait more than that. Yes, the fuel pump will time out, but it will kick in when the regulator drops the pressure, that's not a concern.

 

Guys, just so you know I'm still having conversations with L-N about the alt/GP issue. Not everyday, but we're going back and forth. I'm not sure they know our trucks that well. Not true, I know they don't.

Anyway, last suggestion was to get the alternator output away from the GP feed so the driver's batt will absorb the "surging". I don't see it as surging, I see it as a voltage control issue. As soon as it goes over 14.3 - 14.4 the GPCM kicks out. Then the surging from the GP draw on and off. Thank god CARB isn't reading this.

Latest vid to show them, if they watch.


https://www.youtube.com/watch?v=bR4B-BzZPXk

And you can hear the engine tap/knock that has me worried.

 

Nice video jack. I notice that with the factory pulley the GPCM tries multiple times to bring the GP's back on whereas with the overdrive pulley it only makes one additional attempt after the initial startup turn on.

Hopefully someone at L-N will take the time to realize this as an actual problem and take the time research it. At least with the factory pulley setup anyway

 

Yeah, with the smaller pulley the voltage just stays high enough most times to keep the GPCM from re-engaging. I hope we're starting to get over the "your truck has a problem". It was a long discussion and pictures sent that our trucks don't have a relay but a GPCM, including opening one up showing the electronics.

 

Once that cylinder fires a time or two, there isn't really a need to keep the glow plug energized, compression produces the heat.

 

Exactly what I've been thinking the whole time. I don't see any reason to fuss.

While I'm here: I recently picked up one of these LN alts. for $264 to my door. (don't know if that's good price or not but if anyone is interested I can share where I got it)

Jack, the power pulley from eBay you recommended earlier on was the wrong shaft diameter and offset deeming it unusable. No big deal, I just used my stock pulley. I didn't do any real testing but watching ScangaugeII within a second or two volts come up to 13.8 - 14.2v. I can sense the glow plug load come on and off for the first minute so I'm not really seeing the issue. I know the plugs are coming on because it drops the volts for a second down to 13v or so. But now after a cold start I'm always getting a voltage reading higher than the static battery volts before the start which to me is a good thing.
Also I inspected the brushes on my 70,000+MI rebuilt Alt and there is still plenty of life left. They were barely worn to the holes in the brush that is used for assembling the brush set.

 

Please for all of us who are not going through 16 pages