Low voltage warning and battery issue, need help diagnosing.

[racer24crm]

Ok, so long story short, low voltage warning came up on the dashboard on my way to work. Started car when leaving and it was fine at first, then I get a more serious looking warning to "check charging system immediately". The voltage was down to around 9 volts. I was close to home luckily.

Anyway,I park it in the garage and the negative battery terminal is very corroded. I clean it up and hook the battery back up. Warnings go away, voltage returns to the normal 14.1 to 14.3 volts that I've always had.

I've been driving for the past couple days with no issues but tonight on the way home the low voltage warning came back and the voltage was 10.8.

The car has 55k miles and the battery is 9 months old. Do you think it's an alternator? Car runs fine once it is started which makes me think it's the battery or cables.

What do you guys think?

Thanks.

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[Deleted member 35775]

Alternator might be bad. I had a very similar situation with my 2020 GT350 (2 months ago) and had the alternator replaced due to failing diodes. Fortunately my replacement was covered under warranty.

 

[racer24crm]

Alternator might be bad. I had a very similar situation with my 2020 GT350 (2 months ago) and had the alternator replaced due to failing diodes. Fortunately my replacement was covered under warranty.

I was afraid it would be an alternator. Car is out of the warranty period, unfortunately. I was thinking if the alternator was bad it wouldn't stay running.

This car has been very good to me for almost 7 years now so I guess it's about time it starts to have some issues.

 

[Jackson1320]

If the battery is bad it will not start but once running it will be fine. If alternator is bad it will run until the battery dies. Get a cheap flux and check volts at the alternator. If low clean with carb cleaner and give it a few taps with a hammer see if it works again

 

[Rapid Red]

Have a charger, throw it on get a full charge on the battery. Then monitor, check the both cables again and clean, might not be a bad idea. Remembering it corrected things at first .

By cleaning is the battery post and the inside of the terminal shinny. That's a clean connection.

Usually the alternator is one of two things good or bad, intermittent is unusual.

What's the brand an model of the battery ?

 

[racer24crm]

Talked to my mechanic, thinks the intermittent charging is odd too and it may not be the alternator, might be a bad sensor or regulator.he won't know until he runs some tests. I'm working late tonight so I will try these suggestions when I get home.

Battery is a diehard gold 96R-3.

 

[Rapid Red]

Talked to my mechanic, thinks the intermittent charging is odd too and it may not be the alternator, might be a bad sensor or regulator.he won't know until he runs some tests. I'm working late tonight so I will try these suggestions when I get home.

Battery is a diehard gold 96R-3.

Good, used them before ... good luck

 

[racer24crm]

Tried cleaning the terminals again and checked the wiring out, everything looked good. Still no change.

Charged the battery back up and limped it along to the mechanics garage last night since he's right down the road from me.

Alternator is bad. $475 for OEM replacement and $125 for the labor. Better than I thought it was going to be. Should be back on the road later today or by mid morning tomorrow.

He said it wasn't horribly low mileage to have it replaced but he's replaced 4 other S550s alternators the past couple years with mileage all over the place. Seems to be something that can just go out with no rhyme or reason, according to him.

 

[Rapid Red]

Good work ....

 

[racer24crm]

Follow-up...

My mechanic asked if I had any engine work done because all of the valve cover bolts were loose. The two directly above the alternator were almost backed out all the way. This causes oil to leak onto the alternator and burn it out. He tightened them down, obviously,but he said he doesn't really see that stuff happen on newer cars.

I never had engine work done so I was pretty confused too. He chalked it up to being a Monday or Friday build at the plant. Very strange.

 

[Deleted member 35775]

Follow-up...

My mechanic asked if I had any engine work done because all of the valve cover bolts were loose. The two directly above the alternator were almost backed out all the way. This causes oil to leak onto the alternator and burn it out. He tightened them down, obviously,but he said he doesn't really see that stuff happen on newer cars.

I never had engine work done so I was pretty confused too. He chalked it up to being a Monday or Friday build at the plant. Very strange.

funny you mentioned the "loose" bolts on the valve covers. after the mechanic brought me my car (after the alternator repair), I smelled burning oil. the service mgr and dealership mgr could smell it as well. i opened the hood and you could see it seeping out due to a loose bolt!!! i was pissed!!! i didn't scream/yell at anyone; just told them they lost a customer who purchased 3 mustangs in 3 years. i sent this picture along with my feedback to Ford.

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