battery light symbol flickering on and off, altornator or battery? - Ford Powerstroke Diesel Forum
 
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post #1 of 6 Old 10-21-2019, 08:10 AM Thread Starter
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battery light symbol flickering on and off, altornator or battery?

2001 f350 7.3L 185,000 miles, well kept, maintained truck.

all of a sudden, just twice now, randomly, one time while in stopped on a dirt road, and just now coasting down a short grade, my battery light in the lower left of my dash came on, flickered, then went off again. the first time while stopped, it went on and off a couple times.


batteries are SOMEWHAT new, i do live in warm las vegas so batteries die sooner than most. probably 2 years on the batteries. usually they will go 3-4 here. i do buy decent batteries.


but i am thinking the alternator. any good input out there from folks that have had same problem?

if so, recommendations for new alternators, one that will last another 200k miles?
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post #2 of 6 Old 10-21-2019, 08:22 AM
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more than likely you are loosing a diode in the Alternator

the thing is it is hard to test until it fails all the way

you can give the parts place a try since they can at least test the alt on the truck

batteries are always better tested out of the truck

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post #3 of 6 Old 10-22-2019, 07:16 AM Thread Starter
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Originally Posted by ZMANN View Post
more than likely you are loosing a diode in the Alternator

the thing is it is hard to test until it fails all the way

you can give the parts place a try since they can at least test the alt on the truck

batteries are always better tested out of the truck

thanks! i figured it out, alternator was only putting out a little over 13 volts. i got a good deal on a brand new napa alternator. wasn't my first choice but it was in stock and easy to put in so problem solved
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post #4 of 6 Old 10-22-2019, 09:01 AM
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With the battery cables being 20 yrs old make sure to check them out esp the grounds for both negatives. I flatout replaced both my negatives with oem from riffraff diesel but the previous owner mangled them good. Not uncommon to see a ton of corrosion when pealing back even couple inches of the original cables with their age etc.

Glad you got it figured out and thanks for posting your solution too.

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post #5 of 6 Old 10-22-2019, 09:24 AM Thread Starter
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Originally Posted by JustinOOO9 View Post
With the battery cables being 20 yrs old make sure to check them out esp the grounds for both negatives. I flatout replaced both my negatives with oem from riffraff diesel but the previous owner mangled them good. Not uncommon to see a ton of corrosion when pealing back even couple inches of the original cables with their age etc.

Glad you got it figured out and thanks for posting your solution too.
i will do that, i live in las vegas where we outlawed humidity years ago so I think they are all right, i did look at them but I did not peel back the insulation, and i have seen what you are talking about on other older cars (why can't i afford a new car?) so i will check it out again.

i think i will order all new cables and maybe a starter cable ,,,when i get back from putting the smack down on a big buck. why does my truck always break down during hunting season.

but anyway, at idle the new alternator is putting out about 14.3 volts. the dc alternator puts out 14.8 per the specs on their website, i always thought anything over 14.6 might overcharge and kill batteries sooner.
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post #6 of 6 Old 10-22-2019, 09:33 AM
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Originally Posted by rockwind View Post
i will do that, i live in las vegas where we outlawed humidity years ago so I think they are all right, i did look at them but I did not peel back the insulation, and i have seen what you are talking about on other older cars (why can't i afford a new car?) so i will check it out again.

i think i will order all new cables and maybe a starter cable ,,,when i get back from putting the smack down on a big buck. why does my truck always break down during hunting season.

but anyway, at idle the new alternator is putting out about 14.3 volts. the dc alternator puts out 14.8 per the specs on their website, i always thought anything over 14.6 might overcharge and kill batteries sooner.
Napa has generally been ok for me. Maybe one step above autozone/o'riley quality but sometimes an alternator puts out more initially, then backs off depending on many varibles etc.

The two negative cables were cheaper to buy than make by far and honestly unless you have all the tools and parts on hand so was the positive cable but took me maybe 2 hours to do both negative cables and little over 1.5hours for the positive. Worth it in my mind as the -25 is hard on the batteries so having the best ground/battery connections helps a ton in winter lol.

-99 F250, 4X4, 6.0 trans cooler, 08 mirrors, 05 grill, AIS Intake, lvl kit, JW Vbody, cncfab hpop lines, WW2.

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"Its like me getting five 5 gallon bucks and throwing regular, mid, premium, #2 diesel and offroad diesel and then shooting a roman candle at each one to show which ones burns better."
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