Battery light is on

[exranger06]

The battery light on my Explorer lit up today. I took it for a short drive (about 2.5-3 miles round trip) and the light was on the whole time. I had to pick up my uncle's mail while he's away on vacation. When I got to his house, I turned the truck off and re-started it, hoping that it would disappear. It didn't.

When I got home, I took the battery cables off and cleaned all the corrosion off them, hoping that would fix it. Again, it didn't. The voltage gauge on the dash is right where it should be, and my multimeter is showing a good 14V across the terminals while the engine is running. The battery is showing about 12.75V with the engine off.

The battery is about 6 years old with 36k miles on it, and the alternator is factory original. Should I just go ahead and replace both, or should I do a little more diagnostic work first?

EDIT: Forgot to add, my belt tensioner is really old, pretty likely original too. Probably should have changed it when I did the serp belt a month ago. It doesn't appear to be slipping (no noises or anything) but maybe it is and it's not letting the alternator charge up?

 

[eljefino]

I would start examining the alt connectors, there is something flaky about the ones on fords.

 

[Johnny]

I would have the alternator check first. However, 6-years is a long time for a battery. I had to replace the battery on my wife's Element last week and it's only 4-years old.

 

[J. A. Rizzo]

Most of the auto parts places can load test the battery, meaning put a specific load on it for a specific time and check the voltage drop to determine the battery condition. Checking the alternator output under load is also advisable but might be more work. 6 years is a pretty good time for a battery. Might just be time for a new one. What is the group size?

 

[Smoky14]

Diode

 

[exranger06]

It's a 65 group size. It's a Napa 7565: http://www.napaonline.com/Search/Detail....9+59999+2999999

Kind of annoyed that the parts store is closed and I can't really do anything till tomorrow morning.

 

[J. A. Rizzo]

Originally Posted By: exranger06
It's a 65 group size.


If you need a new one, Consumer Reports rates the Diehard Platinum Group 65 ($190!) as their top Group 65 battery, followed by the AutoZone Duralast Gold Group 65 at $100 and the Kirkland Signature (Costco) 12866 at $75 as the third pick and a Best Buy. The Napa Legend 8465 at $105 comes in 4th.

 

[J. A. Rizzo]

Originally Posted By: Smoky14
Diode


That's true. If you have a way to check the voltage with an oscilloscope with the engine running, you will be able to see if it's a diode problem or not. Are you getting any radio noise or odd electrical issues? Dimming when turning on high loads like a defroster or turning on the headlights with the brights engaged?

 

[exranger06]

UPDATE: All fixed!

Originally Posted By: eljefino
I would start examining the alt connectors, there is something flaky about the ones on fords.


You sir, were spot on! I disconnected the connectors at the alternator, and reconnected them. Started the engine. No battery light! I shut the engine down, and disconnect them again. Noticed one of them looked a little corroded. I cleaned it with electric contact cleaner (OK it was actually carb cleaner, it was all I had

) I left it disconnected and started the engine again. Sure enough, the battery light was back on. I plugged it back in while the engine was running and the light goes off!!

 

[Gary Allan]

Originally Posted By: eljefino
I would start examining the alt connectors, there is something flaky about the ones on fords.


I don't know about the newer units, but both 91 and 93 Taurus would have the light on whether or not the thing was charging. I assumed it was some of the apparently senseless connectors on the alt.

 

[Papa Bear]

I would plan on changing the battery after 6 yrs anyway.

Better to change it on a nice summer day at your convenience rather than a mall parking lot in the middle of winter.

 

[mechtech2]

We have to remember that cables have TWO ends, not just the battery ends.
Why some people clean only one end and think the job is done is beyond me.

 

[exranger06]

Originally Posted By: mechtech2
We have to remember that cables have TWO ends, not just the battery ends.
Why some people clean only one end and think the job is done is beyond me.


Because the battery ends are much more susceptible to corrosion. 99% of the time cleaning the other ends is not necessary. The wire on the alternator that was corroded wasn't even the same cable that goes to the battery.

 

[ahoier]

Originally Posted By: Papa Bear
Better to change it on a nice summer day at your convenience rather than a mall parking lot in the middle of winter.
Something to think about though....I know here in FL; I don't know if it's just the heat, or the "new" manufacturing done of the batteries, but they just don't seem to last as long down here.....avg lifespan is 2 years! Makes me wonder how WM and other chains can offer "3 year Replacements" (and prorated up to 72 months after that!) on batteries and make a profit from them....I know this past winter has been particularly bad on batteries my bud told me, they had about 8 battery returns/exchanges per day on avg (some days 2, others 5, but avg, about 8....lol).

Honestly, I'd run the battery til it's dead

Just in fear of getting a "new" battery, to find it fail on you in 2-5 years....

I know WM can do a load test in their shop to test the battery and alternator, generally if you have a "battery" light on your dash, it's an alternator issue though....

Now the belts/tensioner, sure, go ahead and replace those just to be safe