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Electrical issues

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#1
Hi, this is my first post. I have a 2014 fiesta st that since about october has had significant charging issues. At first I thought bad alternator, I've load tested the battery etc. so the basics can be ruled out. the car typically charges 12.6 volts with the alt sensor wire connected. when its disconnected (bypassing smart charging I guess), the car charges 13.8 no matter the load. I've been doing this to get by but I still frequently have issues and think this may just make the problem
worse. Any pointers are greatly appreciated, I'm shaky with electrical but trying to learn what I can.

also, the issue can be intermittent and rn the car is charging almost 15 volts with alt sensor wire connected.

-augie


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alexrex20

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#2
What exactly is the issue you're experiencing?

The Fiesta ST uses smart charging logic and only outputs on demand. If the car starts and drives normal, then there's no problem. Quit looking for one.
 


OP
A
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Thread Starter #3
believe me, there's one. but it's intermittent. where's this logic decided, and could bad feedback "based from demand" cause the car to think the battery is overcharged when it's not bringing it to 12.6. to be clear, I have had to jump the car 50+ times over this period. its a miracle the battery isnt depleted. thanks. are there any schematic showing this smart charging pathway. I know there's a sensor on the negative terminal of the battery, but beyond that it's unclear (to me).


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OP
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Thread Starter #4
I should've made it more clear that the car does start and drive normal, but only with the default charging voltage of 13.8 bypassing smart charging. which computer interprets smart charging parameters? the ecu?


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OP
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Thread Starter #5
Krug this is huge! thanks!


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OP
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Thread Starter #7
Great....Yep me too. Take care


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alexrex20

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#8
All signs point towards your battery. Load testing will look for a dead cell but it won't show you if the batteries reserve capacity is severely diminished. Quit overthinking it. Reconnect the alternator and let it run like it wants to, put a new battery in it, and I bet everything is fixed.

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OP
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Thread Starter #9
so are you suggesting a bad battery could confuse the smart charging system into undercharging the car? Just making sure I follow.


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alexrex20

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#10
The smart charging is not confused at all. It only reads battery voltage and load, and determines if it needs to charge or not. There is no way for the computer to know the condition of the battery. All it knows is battery voltage. If your battery has been jumped 50+ times, get a new battery. Repeatedly draining a battery causes the plates to sulfate which inhibits the current flow across the plates. Reserve capacity is the rating for how long the battery can sustain a given draw while still maintaining sufficient voltage to start the car. Typical batteries for cars/trucks will have a reserve capacity of around 1.5-2.5hrs. But each time you drain a battery, the low voltage allows sulfate buildup on the plates. It just gets worse and worse every time. If you've had to jump start your car 50 times, the battery is TOAST. The reserve capacity is probably just a few minutes at this point. Just replace it and move on with your life.

Quit overthinking it. A battery can only accept so much charge. The fact that your alternator turns on and off but your battery does not last, does not mean your alternator or its associated software is bad. It means the battery is maxed out. Replace it.



ETA: The car is not undercharging your battery. It is charging it as much as it can. Your battery simply will not accept it.
 


Ford ST

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#11
If your 2014 still has the original battery I would definitely look at replacing the battery. Just put a battery in it and see how it goes it's a five year old car.

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me32

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#13
Im sure the. Battery is toast if its original. A 2014 built in 2013 is now a 5yr old battery.
 


OP
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Thread Starter #14
not sure if anyone cares, but I replaced the battery today. it needed to be replaced (sulfation) as others have mentioned. however, I'm still having the same symptoms. I'm going down the line (hoping not PCM lol), curious what kind of resistance others have in their battery voltage sensor. the car was charging nearly 15 volts on a new battery with signal wire connected. unplugged the alt sensor wire again to return to default 13.8 cause 15 will damage the new battery no doubt. curious what others think/ if they can measure this voltage sensor for comparison (on negative terminal cable)

thanks


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alexrex20

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#15
those are symptoms of a properly working charging system. quit looking for problems when there aren't any. ~14.7V is normal output for an alternator on a lead acid battery.
 


Ford ST

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#16
those are symptoms of a properly working charging system. quit looking for problems when there aren't any. ~14.7V is normal output for an alternator on a lead acid battery.
He is right 15V is fine. 14.7V is very very normal.

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OP
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Thread Starter #17
but I really want there to be something else wrong!!! ok I'll keep an eye on it. thanks for the expertise guys.


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alexrex20

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#19
15v is ok per the service manual. Over 15.9v then worry. Good luck throwing parts at it and hoping for the best or run test per the service manual to have a better clue.

I'm still on a 2014 OE battery that's coming up on 5yrs soon.

https://www.fiestastforum.com/threads/17078-Battery-Maintenance


mine lasted 1.5yrs but that's certainly not the norm. 5-7yrs is about average in my experience. my Nissan has a battery from an M1 Abrams and it still cranks right up. the battery is dated 2003 lol
 


OP
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Thread Starter #20
you just never know I guess. I'm gonna keep an eye on it for awhile but hopefully home free. interior cabin lights flicker with hazards on but its subtle enough that I cant remember if its always done it. anyway. enjoy the fun winter driving. snowing here in chi area woo


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