Charging System Service Now - Argh

[galaxy]

The voltmeter in my car is hands down the most unused gauge. Never look at it. You’ll drive yourself bonkers trying to figure it out. I know more than one that have swapped out perfectly good alternators due to gauge readings alone. I figure if there’s ever a true electrical problem, the car will tell me. With an electrical problem, there will always be more than one symptom, always. Gauge alone is not one.

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[Angrey]

The voltmeter in my car is hands down the most unused gauge. Never look at it. You’ll drive yourself bonkers trying to figure it out. I know more than one that have swapped out perfectly good alternators due to gauge readings alone. I figure if there’s ever a true electrical problem, the car will tell me. With an electrical problem, there will always be more than one symptom, always. Gauge alone is not one.

Thanks to the EPA, the Ford BMS system is incredibly estoeric and unnecessary and schizo. Depending on a whole host of conditions (RPM, battery charge, usage/demand) the voltage will bounce around and just when you think you haven't the algorithm figured out, it'll do something different. I agree, attempting to diagnose problems using the system voltage readings is spurious at best, unless the voltage is simply WAY out of range high or low.

You might have noticed that there's an increasing number of troglogytes on the highway at night with no rear running lights. That's because the geniuses at the automotive industry combined with our illustrious government decided that when you run daytime running lights, they didn't want to suffer the microscopic decrease in efficiency by having the rear lights on as well. So what ends up happening is a dumbass sees the lower output DRL's on and thinks their lights are on, all the while the car is basically blackout from behind. Canada is now fixing this going forward and I imagine NHTSAA will address it as well.

For one I never believed that DRL's add any level of safety. Certainly not an uptick that corresponds with the decrease in safety of having no rear lights on. But that's government idiots for you. And the BMS system follows that bullshit. Attempt at every possible juncture to reduce the load on the system (and eek out that extra economy). I miss the old days when the alternator ran and a simple voltage regulator was all you needed.

 

[Basspro302]

Did you replace the bms sensor?

 

[Evolvd]

JS Alternator makes higher amperage units for Mustangs. They all use the same two alternators and only difference I’ve found is between cars with and without seat coolers/heaters.
Have you check the Hall effect sensors? There’s one on the batt to chassis ground and another on the alt to fuse block. Try disconnecting both of them and see if the BMS freaks out again. I had all these issues with the Anitgravity restart battery and had to return it. I’m now using a XS Power D4700 and it’s given me zero trouble. It also fits under the battery tray which some folks have said it doesn’t…but it works fine for me.
Also, have you done a static amperage check? You’ll need an amp meter and let is sit overnight to see how much it’s drawing just sitting there.
Beyond that, it may be time to have Ford diagnose it so you stop wasting money on parts that don’t fix it.

 

[ChipG]

It's not the voltage gauge having me chase things, it's the "Charging System Service Now" error that pops up within about 5 seconds of turning on the car. As far as having the dealer diagnose, I had a dealership "fire" me as a customer because they couldn't diagnose the issue last time (which I fixed by replacing the alternator pigtail). Now that I'm in powertrain warranty only, I'm not going to pay dealer rates to have them throw parts at it. If parts are going to be thrown, I'll use my own zero cost labor at least

 

[ChipG]

I'm at my wit's end. Recap:

Behavior: "Charging System Service Now" light pops on within about 5 seconds of startup, stays on steady for the remainder of the time the vehicle is running. On one drive (unclear what made this drive different), the center stack, HVAC, and other power shut down, and AdvancTrac disabled.

Checks and attempted fixes:

• Voltage meter on dash typically jumps up to ~15.2V after startup, settles into mid-14V range steady. On the one drive, voltage meter went completely crazy.
• No voltage drops anywhere in the fuse box.
• Forscan shows slight difference between battery voltage requested and system voltage (14.56V vs ~14.8V - 14.9V respectively). This is after pigtail and battery replacement, before alternator replacement.
• Visual and manual inspection of wiring harnesses, grounds, and connections that I can find shows no obvious issues. Connections are tight, non-corroded.
• Replaced the alternator voltage regulator pigtail. No change in behavior.
• OEM battery read low after sitting. Replaced the battery with a fully charged AG ATX20-HD, performed the BMS reset several times (both non-Forscan and Forscan versions). No change in behavior. (To be clear, the one time the system went crazy was after battery replacement).
• Replaced alternator. No change in behavior, though I haven't driven the car around since this, just driveway start and idle testing.

At this point, the starter is relatively new. Battery is new. Alternator is new. All seem to function well (starts easily, battery holds voltage, alternator puts out proper voltage). Alternator pigtail is new. I'm not sure what else to do. The only other info I've found is a post on TMO indicating that there is a main wiring harness that tends to fry. I have no other ideas than trying to replace that as well.

Any ideas? Specific connectors grounds to check? Specific Forscan checks? Specific voltmeter checks? Otherwise, I will indeed throw another part at it and put the harness in. If I have to go to a dealer, I can try that, but my confidence is low in that path. They refuse to diagnose without all OEM parts (so I'll have to reinstall the alternator and the possibly-failing OEM battery), and last time this happened they failed completely to figure out the issue (though different dealer). If they just go fishing, the labor and parts are on my dime with no guarantee of a fix. My suspicion is they will likely want to replace everything I've already tried with new OEM parts and labor, which is a waste of time and money.

This issue is driving me nuts, and I have a race this weekend.

 

[ChipG]

Additional updates:

• Every time I try to drive the car now, within 5 minutes the voltage goes crazy, spikes as high as 17V, the center stack powers down, and AdvancTrac disables.
• I disconnected the current sensors to disable BMS and it made no difference in behavior.
• DTC code is P0625: Generator Field/F Terminal Circuit Low

I have the OEM battery charging now to make sure it's fully charged and will try putting it back in tomorrow to see if anything changes, but the behavior still feels like a voltage regulator issue. I'll take yet another look at the pigtail again tomorrow as well. I don't know what else to do other than replace the whole engine harness.

 

[ice445]

Sounds like a harness or pcm issue at this point unfortunately. Since you say it takes a bit to act up, it may be thermal expansion related.

 

[Egparson202]

I had similar experience but it was remedied with the steps you’ve taken. I had a much less severe instance at my last event which was remedied with battery charging.

Do you have the OE VDM or DSC Sport controller?

 

[ChipG]

I had similar experience but it was remedied with the steps you’ve taken. I had a much less severe instance at my last event which was remedied with battery charging.

Do you have the OE VDM or DSC Sport controller?

It's OE.

 

[Egparson202]

Any chance you have a Bluetooth dongle on the OBD2 port?

 

[ChipG]

Any chance you have a Bluetooth dongle on the OBD2 port?

I sure do. Running with it disconnected hasn't helped, though.

 

[Egparson202]

I asked because I used to leave my BT dongle connected between events and concluded it was drawing power and resulting in low charge state. Any time the battery is not happy the system is also not happy. Very sensitive in my experience. Possibly the conventional battery is slightly less so, but the whole thing is only as strong as the weakest link.

TBH, it seems unnecessarily tempermental. @WItoTX found some correlation between ATX-20-HD vs OE battery when using a DSC Sport controller. I’m not having that problem (right now) but I did have one instance that was solved with a fresh charge.

 

[WItoTX]

I sure do. Running with it disconnected hasn't helped, though.

In my case, I could start the car no issue with the ATX-20. However, pushing the car AT ALL, the car threw a fit, and a host of electrical systems shut down, including power steering.

The voltage swing you are seeing, is it indicated on the dash, or are you watching it on the volt meter? You probably already know this since you have been chasing it a while, but the dash indicated number is what the alternator is putting out, not what the battery is charged to. I never had an experience where 17 volts were indicated. You could test the battery by letting the car sit for a day, with the doors locked (this made a difference in my case, some systems continue to run if unlocked), and the key stored at least 30' away. See how much power drop there is over a day.

Two things I would try:
1. Find someone with a fresh battery at least as big as the factory battery, throw it in and see what happens.
2. Check the ground lugs. there is one under the intake box, but its not uncommon for the negative lug on the passenger side strut tower to corrode and lose a good ground. Pull off that ground, sand it/steel wool it down to bare metal, and reconnect. Then go from there. There is also several grounds in the passenger fuse box, you can pop the cover off and make sure they are tight.

Sorry wish I had a better answer for you. Nothing worse than electrical issues. I chased mine for about a year before I realized it was the battery.

 

[ChipG]

So, some progress. I swapped the fully charged OEM battery back in. The "Charging System Service Now" notice still pops up within 5 seconds, but in ~5 minute test drives with and without the current sensors in place the system didn't go nuts and shut down as it had very quickly on the same drives with the AG battery. So, perhaps I'll at least be able to run this weekend while I chase the wiring issues. It remains to be seen whether the AG will cause any problems with the rest of the system healthy.

Later today - fully checking (removing/cleaning) all the grounds as suggested, and re-checking the alternator pigtail.

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