Charging Service System Now please help.

[Nolen117]

We’re back at it with this car lol.

I get a warning on the dash in red saying "Charging System Service Now". Then it told me "turning off low battery functions.”

P0625. Willing to bet its the alternator

It starts fine but still get the warning. It was a steady 11.9v.
Yesterday morning i made it 15min down the road and was suddenly getting 9v. Turned it off and to no surprise it failed to start.
Jumped it and had a consistent 14.1v for the 30min drive to work. Which this having Fords smart charging system, the alternator only gives power when the battery needs it so it shouldn’t need 14v just cruising.
3 hours after I got into work i had to run an errand and it was at 11v again.

Well, now the battery, alternator, and starter tested good as per Oreillys. The battery was at 8% and had to be charged. The past three days it hasn’t been charging at all.
This morning the multimeter got 12.4v from the battery terminals. When starting, it dropped to 10v, 11v and stayed there. With the blower on full blast, brights on, and radio going, i was at 11v.

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[Egparson202]

The BMS complicates the troubleshooting process on the charging system. May be something as simple as a battery on its way out. Or an alternator. When mine gave trouble (like you) it all tested fine. Was not fine. Tradtional thinking for late-model Mustangs is that the batteries are suspect. So I threw a battery at it but that wasn’t the problem. For me (different symptoms) it was a bad connector in the wiring harness to the alternator. Dealer diagnosed and fixed after my Indie shop was stumped.

 

[Cory S]

Battery @ 12.4V at rest signals the battery is OK after sitting overnight. Alternator is probably shot. Is the induction ring still around the ground cable?

 

[Cobra Jet]

^^^ Good advice.

Just to add some more tech:

The newer Ford alternators from 1994+ should have an external voltage regulator mounted to the back side. It contains brushes in it, similar to a slot car motor. Over time those brushes wear down. Now depending on how many miles are on the car, the brushes could be at their end of life use.

It's cheaper to replace the voltage regulator than the whole alternator. It's also very easy to replace as well. See if you can source a voltage regulator first before deciding to replace the whole unit.

Yes there are other internal parts of an alternator that can go bad - but usually the voltage regulator is the first to go because those brushes were out, causing voltage/charging/continuity issues.

If the alternator is making any screeching or chirping noises, then the internal bearings are shot, therefore yes, I would replace the whole unit.

 

[5doorsoffury]

I believe there have been threads on bms issues some unplug the current sensor located by the battery cable that the system uses to detect low power( current sensor) and sink your boat.

https://www.mustang6g.com/forums/threads/battery-management-system-reset.106897/

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