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Discussion Starter · #1 ·
I thought it was time I stopped hijacking the other thread where @f64 seems to have successfully upgraded from a 150A alternator to a 250A alternator. There were great instructions and it seemed like it would be very easy to do. I read over it a few times, read through the service manual, bought and waited for an alternator, and then finally did the swap and ....

Apparently I don't have the same sort of luck.

Refer to the previous thread here:

Here's a summary of what I've done:
  • Replace OEM battery [ https://tires.costco.ca/Batteries/Product?ItemNo=270552 ] (Note: The battery specs seem ok, but this battery is much smaller than the OEM version and may require some additional packing to keep it from moving around in the battery box. I have known this was needed for quite a while, as listening to the radio for 30 min or so could cause me a no-start.)
  • Remove assumed-original 150A alternator, install re-manufactured Remy #23038 250A alternator (about 2 hours on my back under the van with only wrenches and socket set)
  • Used FORScan to change "Alternator" setting from 150A to 220A (Have also tried it back at 150A and "not configured" with similar/same results)

Shortly after starting and running for the first time following the replacement, I received first the DTC:
P065B, "Generator A Control Circuit Range/Performance"

With the addition shortly thereafter of
P0625, "Generator Field/F Terminal Circuit Low" and
P0626, "Generator Field/F Terminal Circuit High"

And at some point the "red battery" charge system malfunction indicator lamp turns on. I may have seen it go off again at some point, but it always returns.

Monitoring the battery voltage, it seems that it is low - about 13.4 when my 50A charger is running, and maybe 13.8 with it turned off. It's hard to tell on a digital meter but I think the voltage is jumping around, maybe between 13.2 and 14.2 or so. I'll see later if I can narrow this down better or see any correlations.

In the meantime I'm going to go through the service manual and see how many of the pinpoint tests are feasible, plus try to learn exactly how the system is supposed to be working. It may require re-installing the original alternator to get some "good" readings. I've really worked that poor thing pretty hard though, so there's no guarantee that it's in pristine condition. I'm trying to sort through this problem eliminating variables because there are way too many right now to make any sense of things.

I may also give Remy a call as was suggested in the other thread. I'm doubtful this will prove useful, but who knows?

-- More to follow --
 
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Discussion Starter · #2 ·
Attached is some good information for anyone else trying to troubleshoot charging system problems or make custom modifications.

A very interesting paragraph stuck out for me:

153832


This describes my situation quite accurately, so it seems likely it's running in a default "limp home" mode. But exactly why this may be the case I don't know yet.
 

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Discussion Starter · #3 ·
I'm also reading (again) about the idea that any customer loads should be grounded to the chassis rather than the negative battery terminal. So far I have not been following this instruction, and I acknowledge that there's a chance this is part of what's causing my issues.

I just don't see how this makes a difference though. The battery negative terminal is, as far as I can tell, directly connected to the chassis at G309. If there was a sensor somewhere on the cable between the battery terminal and the chassis, I'd readily accept this admonition. But there are no indications that this exists! Thus I maintain that it is electrically identical (ignoring negligible resistance differences) connecting to the negative battery terminal or the chassis.

153838
 
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Discussion Starter · #4 ·
Here's another useful document I've come across while trying to learn about the system. Apparently the 3-pin system used in the 2018 Transit (GAS ONLY, diesel is different!) has been around for quite a while and is used on lots of other vehicles too.
 

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Discussion Starter · #5 ·
So, the way I understand it is that the PCM can command the alternator's voltage regulator to produce a given voltage through the GENCOM signal, and the alternator provides load feedback through the GENMON signal. With this in mind, I'm thinking that the control and feedback signals might be the same between the 150 and 250, and if anything actually chances with the "alternator" setting, it's in the strategy that's used.

I've learned less about the "sense" signal and how it is interpreted by the PCM.

I have a few things to pursue and I'll follow up if/when I learn anything new on this.
 

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Well, all I can tell from your posts is you have some kind of issue.
What I will add is this. your Delco Remy Rebuilt may be "Newbroke". We see out of the box alternaters not work correctly all the time. Bad choice going with rebuilt, just sayin".
Good Luck!
 

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Man, sorry to hear about that Sparky. I'm going through my own bit of headache with charge controller and inverter pre-charge circuits. Hang in there!

I have plans to install a second alternator next month, and part of the strategy was to avoid messing with the OEM system for this kind of reason. But there's still plenty that can go wrong with my system. I'm also using the battery negative terminal, so if you find out anything concrete on that, please let me know. I can always create a ground point. Maybe just to eliminate future troubleshooting concerns, I will.

Cheers.
 

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...I'm also reading (again) about the idea that any customer loads should be grounded to the chassis rather than the negative battery terminal. So far I have not been following this instruction, and I acknowledge that there's a chance this is part of what's causing my issues...
You are being quite thorough in your troubleshooting (y)
If possible, temporarily pull all the added grounds off the battery and see if it yields different results.

If so, that would be useful info for the many threads that discuss/debate grounding points.
 

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So, the way I understand it is that the PCM can command the alternator's voltage regulator to produce a given voltage through the GENCOM signal, and the alternator provides load feedback through the GENMON signal. With this in mind, I'm thinking that the control and feedback signals might be the same between the 150 and 250, and if anything actually chances with the "alternator" setting, it's in the strategy that's used.

I've learned less about the "sense" signal and how it is interpreted by the PCM.

I have a few things to pursue and I'll follow up if/when I learn anything new on this.
The voltages you are seeing seem to be consistent with the Remy document as to the default voltage when the PCM communication is not working. Given your PCM was OK before the swap means that Gencom is ok. So is would seem to me that the Genmon signal from the alternator may be the problem. But I am sure you are already there!

I did wonder how the connector worked to control the alternator. I thought it had to do with the SRC on 2020+. But now I thinking that the wiring may be the same as the older Transits and just the programming of the PCM is different. Yes, it is quite surprising that this type of control goes back over 20 years! Initially in a Windstar of all things no less. It does make one wonder why SRC was only added in 2020 though.
 

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Discussion Starter · #10 ·
Well, all I can tell from your posts is you have some kind of issue.
What I will add is this. your Delco Remy Rebuilt may be "Newbroke". We see out of the box alternaters not work correctly all the time. Bad choice going with rebuilt, just sayin".
Good Luck!
I haven't had any issues I can recall with remanufactured parts in the past, which is why price dictated the decision here.

Trying to determine whether the "new" alternator is functioning correctly is high on my list.
 
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South main auto on YouTube had a decent theory and operation discussion on the Ford charging system. Most of it is pretty much what you already know by reading the service manual information. His particular case is not the same problem as yours, but I think his discussion might be useful to reinforce or clear up what’s in your manual. By the way, since you are in default charging mode, any chance you forgot to plug in/fully seat the 3 pin connector?

 
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Discussion Starter · #12 ·
By the way, since you are in default charging mode, any chance you forgot to plug in/fully seat the 3 pin connector?
Always a good idea to check the basics first. In this case however, it isn't as simple as a forgotten connection. I've been back in the engine compartment since, and done the first few pinpoint tests. I had to start by disconnecting the 3-pin connector. 😉
 

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Sorry that I didn't see your postings in the other alternator thread until yesterday. I am not sure why the forum didn't bring that to the top.

Anyway, I am still reading your information in detail, but don't underestimate the influence of the starter battery capability (or not) on the system voltage stability and spikes.

As an example, on my test stand I was using:
  • a very decent size 24 / 80 amp-hr AGM to simulate a starter battery
  • Sterling BTB charger that pulls at 70 amps nominal
  • 75 amp / 12 volt rated battery charger that really does push 75 amps

There are some interesting effects of the sterling trying to turn on "hard" and the charger having some small time delays in reacting to the load that made it impossible for me to make this work.

I switched it out with a 100 amp-hr AGM (same brand / lifeline ) and it all started to work, I assume due to the higher buffering effect of the larger battery.

Similarly, there are time constants in how all of these devices and sensors react, some soft start, some go full on, and a battery is not an infinite source and sink of power.

I am actually very impressed that the Ford engineers figured out how to push 2 x 250 amp alternators of power through a couple of starter batteries and keep it all stable.

_

My point I guess is that perhaps test adding back in more starter battery capacity if you have access to something like that for a test. It might help with dampening out some of the instabilities. Obviously just speculation on my part. If you lived closer you could just stop by and test it.
 

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Discussion Starter · #14 ·
(y) I had to roll back to an older version of Forscan to enable the TBC added to my 2015.
So, did you have to do this because the setting wasn't there or because you changed the setting and it didn't do anything? The settings exist for me. I just have no way of knowing whether it actually changes the way the alternator is controlled and monitored.
 

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Error Code P065B is defined as Generator Control Circuit Range/Performance. ... This means the battery voltage needed to power up the generator field coil (to produce amperage) is supplied only after the PCM has input the right signal to a relay or auxiliary control module
.


Error Code P0625 is defined as Generator Field/F Terminal Circuit Low, meaning there's a problem detected in the generator field control circuit, often caused by too shorted connectors or defective CAN bus. ... The F in the description means the Field Coil Control circuit is at fault
.


Error Code P0626 is defined as Generator Field/F Terminal Circuit High. This means there's a fault detected in the generator field circuit, usually caused by a defective alternator, battery, wiring, or poor communication between the control modules. ... The armature spins inside the field coil, which the battery energizes
.

I would try it with a new fully charged OEM battery and all your after market accessories unplugged.
Verify good battery connections.
Run your grounds as Ford suggests ( not on the negative battery terminal )
Then see if it works .
If still not working , swap in a new 240 amp alternator.
Personally if that didn't get it working I would give up and put the 150 amp alternator back
on , return or sale the alternators.
 

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Discussion Starter · #16 ·
I don't know it I'm on the right track, but it seems the logical way to go here...

I visited a local alternator/starter shop early this afternoon and first had my existing 150A alternator bench tested. It received a clean bill of health, so I can be fairly confident putting it back on the van. (Thanks to @Michael Ophus for that suggestion. It yielded some very useful information). The guy there also repeated what was stated above, that there are A LOT OF CRAPPY REMAN UNITS that go out. Had I heard this ahead of time I probably wouldn't have taken the risk. Now I know and my future actions will reflect this information.

He connected his "test box" to the 250A alternator installed on the van, and gave a somewhat tentative "pass" for the unit, as he could control it. But he did say that the output didn't seem stable and that (because it's a digital unit) it was hard to tell anything more detailed. At this point I think I'm chasing an intermittent fault with the GENMON output of the alternator's voltage regulator/controller. This seems most likely, but I still can't rule out that there's an incompatibility with the swap. I'll reiterate that changing the "alternator" setting between 150, 250, and "not configured" doesn't seem to make an appreciable difference in how things are functioning. FORScan doesn't give great resolution or controls on it's graphing/plotting, but if anything I think the setting might just change some of the calculated load percentages. I have to make a lot of assumptions here because I can't know what the PCM is doing with the information.

I've been taking some more screen captures of FORScan, and this one seems to illustrate what I think might be happening:
153856


153858


If you look at the fault indication signals GENMON_FS (bottom green) and GENMON_LS (bottom cyan) you see that they keep ocurring, and it's hard to see with the plot resolution but seems to be flagged when GENMON isn't closely mirroring GENCMD (like it should).

Is there anyone with a similar setup to mine (2018 3.7L) but with 250A alternator that could run a similar plot while idling so that I can have a "good" comparison? I'd really appreciate it!

I have also been seeing frequent "spikes" in the GENMON_HZ readings that I assume are a maximum value. Since the FORScan plot is automatically scaled, this huge spike dominates the plot and the others are hidden in the noise level. Very shortly after the spike the malfunction lamp (GENFIL) is turned on. Though GENFIL doesn't directly correspond to the lamp it seems. The light goes on and off (though very slowly - like multiple minutes) even though the GENFIL signal stays on. Odd indeed, and doesn't help with pinning things down. In the screenshot below I'm adding loads (headlamps + fan) at idle:

153859
 
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So, did you have to do this because the setting wasn't there or because you changed the setting and it didn't do anything? ...
Because the Key Code parameter was no longer there when I knew it had been before, not like the alternator option you are dealing with.
 

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Discussion Starter · #18 ·
I've swapped the 150A alternator back in. Remembering to time it this time, I can report a pretty impressive 35 minutes from battery cable disconnect to reconnect. I didn't even wait for it to cool down entirely.

Wrenches:
7mm - top stud hex end
15mm - belt tensioner, top alternator nut (deep socket would have been better but I didn't have one), bottom bolt if the belt is in the way
16mm (as extra leverage hooked into the 15mm to swing back the belt tensioner, other sizes acceptable :))

Sockets:
10mm - battery terminal clamp nut
13mm deep - alternator B+ nut
15mm - lower alternator bolt if the belt is removed

And I think that's it. The connector comes off if you squeeze the tab with a strong finger while pulling gently.

It helped that it wasn't raining this time, as I didn't look at the ground and sigh each time before dropping down and scooching under the van. Is there a word for laying on your back and walking with your shoulder blades? Maybe we need one.

If there's something to carry a spare of to replace in the middle of nowhere, an alternator would be of high value and should be high on your list!
 
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Discussion Starter · #19 ·
Immediately after putting the 150A back on, I made two plots. One with the "alternator" setting still at 220A, then one with it changed back to the original 150A. Nothing went up in smoke, no horrible sounds were emitted, and no codes were generated in the short time I was monitoring it. The two plots look almost identical. I thought there might have been a 5% difference in GENMON%, but looking at the first (220A) the RPM was higher to start and near the end it comes down to regular speed and matches the second (150A) just about identically. I remain skeptical that this setting changes the way the alternator is controlled. There may be other things it does that aren't so obvious though.

Oh, and the stability of EVERYTHING I'm monitoring is SO MUCH better than what I was getting with the 250A installed.

153870


153871
 
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Discussion Starter · #20 · (Edited)
I figured I should record as much data as I could before removing the presumed faulty 250A alternator, so I made up a quick little wiring breakout pigtail and attached my oscilloscope to GENCMD and GENMON. I'll see about posting them later if it shows anything worthwhile. I also scoped the output/battery voltage and saw that with the connector disconnected (default mode) and no extra load, the output was pretty stable at 13.5V (the default mode). With it reconnected, it tended to ramp up from 13.2V to 14.3V then quickly drop down again. On a digital meter this is averaged out but it's still noticeable that the voltage isn't stable. When everything is working well, the voltage is very stable, like within 0.2V or so.

I did call Remy technical support and the guy wasn't very useful. He took a stupidly long time to find a troubleshooting flow chart and (like usual) I was already miles ahead of where he was starting after having performed most of the pinpoint tests from the Ford service manual and monitored various signals with FORScan. Sometimes I wonder what it would be like to be the person who's not more educated than the tech support person...

Anyway, looking into what it would take to return the alternator to Rock Auto (I think I'm on the hook for return shipping), then the consideration that I'd get a replacement reman of similarly dubious quality, I'm strongly considering having the reman re-remanufactured (is that too many re's?) by the guy at the starter/alternator place. He thinks it's likely replacing the regulator/controller would solve the problem. At the same time he can look over everything else (and I'm fairly sure he'd do it more methodically/reliably) and I should end up with a good 250A alternator for another hundred bucks or so - still assuming that the problem isn't somehow a compatibility issue, of which I have no way of knowing without trying it out.
 
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