Battery or Altenator
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Freshman User
Joined: May 2009
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Battery or Altenator
First off I have a 03 F250 5.4. I ran into Target on the way home from work and went out and the truck wouldn't turn over and the battery died completly. I have never had a problem with the battery before. I have 48,000 miles on it and it is the original battery. My father-in-law tried to jump me and the truck would start, however as soon as he took the cables off, the truck would instantly shut off. Any advice would be great.
Junior User
Joined: Jan 2011
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I'm sure there are bigger hats than mine around here... but it sounds like the alternator to me. I went through two in a short summer long ago, the first died while I was driving down a mountain road, the second when I stopped to make a left turn at a stoplight. Jumping didn't help and had to replace the alternator (twice). The second one was a factory problem so didn't cost me any more.
It might be worth pulling the battery and trying another as a test to see if it keeps running or not. If you know the "new" battery is good and it still won't run, I'd be thinking it was the alternator.
Good luck!
It might be worth pulling the battery and trying another as a test to see if it keeps running or not. If you know the "new" battery is good and it still won't run, I'd be thinking it was the alternator.
Good luck!
Posting Guru
Joined: Mar 2005
Posts: 2,060
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From: Burnsville, MN
Well I don't know that I can speak to the modern generation of vehicles, but it used to be that you didn't need a battery in order to drive a vehicle, just to start it. In other words, there was no reason you couldn't remove a battery, yet have the vehicle continue to run.
If this is still true, the problem should be in the alternator, which most any parts store will test for you for free. Of course, given the age of the battery, now that its been completely depleted, its probably toast too.
If this is still true, the problem should be in the alternator, which most any parts store will test for you for free. Of course, given the age of the battery, now that its been completely depleted, its probably toast too.
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
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From: Stephensville WI
From your description the battery is not charging. You need to figure out why.
It could be the alternator not putting out power, the battery not taking the charge or the even the cables got so corroded the current cannot get from the alternator to the battery or rest of the truck.
Chances are it is the alternator. I would pull it and have it tested at your local national chain auto parts store that can test these things..
It could be the alternator not putting out power, the battery not taking the charge or the even the cables got so corroded the current cannot get from the alternator to the battery or rest of the truck.
Chances are it is the alternator. I would pull it and have it tested at your local national chain auto parts store that can test these things..
Elder User
Joined: Mar 2010
Posts: 544
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I'd bet a benjamin it's the alternator. Same deal on my 00 Chevy, but the battery wasn't dead. I'd start it, it'd cut off battery power and switch to alternator and die. Just start and die as soon as I let off the key. New alternator and I was good to go. Sounds like these trucks will get juice from the battery if the alternator output is low. Good to get you off the side of the road should your alternator go out. Just put in a fresh one and get to cover.
Don't you hate it when they give you no warning they're going to break on you?
Don't you hate it when they give you no warning they're going to break on you?
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Post Fiend
Joined: Jul 2005
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I am pretty sure a modern PCM will not work without the battery there.
So test is not definitive.
Try to measure alternator output with a clamp on ammeter, and simultanously measure voltage to get the wattage output.
If it is within 60% of max rated at 2,000 rpm, you are probably at minimum good to go.
e.g. a 110amp rated puts out at least 60% at 2,000 rpm (try a bit higher rpm as well)
The assumption is battery is flat... and you are just using all the juice you can generate (that is done by turning on everything electrical on in vehicle).
So test is not definitive.
Try to measure alternator output with a clamp on ammeter, and simultanously measure voltage to get the wattage output.
If it is within 60% of max rated at 2,000 rpm, you are probably at minimum good to go.
e.g. a 110amp rated puts out at least 60% at 2,000 rpm (try a bit higher rpm as well)
The assumption is battery is flat... and you are just using all the juice you can generate (that is done by turning on everything electrical on in vehicle).
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FTE Leadership Emeritus
Joined: Sep 2000
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From: Stephensville WI
From memory:
Disconnect negative battery terminal.
Remove air intake duct, if in the way.
Relieve tension on serpentine belt, slip belt off of alternator pulley.
Disconnect alternator wiring.
Remove mounting bolts and remove alternator.
To install, work backwards. It is also a good idea to put the battery on a charger while you are working on the alternator (away from the truck) so it will have a charge when you are done.
Disconnect negative battery terminal.
Remove air intake duct, if in the way.
Relieve tension on serpentine belt, slip belt off of alternator pulley.
Disconnect alternator wiring.
Remove mounting bolts and remove alternator.
To install, work backwards. It is also a good idea to put the battery on a charger while you are working on the alternator (away from the truck) so it will have a charge when you are done.
New User
Joined: Apr 2010
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Yeah I go with the opinions too, alternator sounds about right! and although you may want to save money, it may be time to buy another great battery! Mine runs on duralast gold 8 yr warranty battery. Died on me once, zone gave me a new one back for low$....
changing the alternator is simple as edford described, just watch your hands as you release the torque on the nuts and screws and use a good rachet. Remember to grease up the contacts on the battery and do a cleanup on the terminals while tightening them back up. Just a thought ;-) Hope it helps!
changing the alternator is simple as edford described, just watch your hands as you release the torque on the nuts and screws and use a good rachet. Remember to grease up the contacts on the battery and do a cleanup on the terminals while tightening them back up. Just a thought ;-) Hope it helps!