How do tell if the Alt or Battery is bad?
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MMNC (SS)(Ret)
Joined: Mar 2004
Posts: 11,606
Likes: 149
From: SE Georgia
How do tell if the Alt or Battery is bad?
Battery volts went to <8 volts and the truck died. Got a jump and kept RPM high enough to maintain 9-10 volts until I could get to a store and buy a $130 battery. Got her home. But now battery volts are hanging 11.6-12.1 volts. Not going up, but not going down.
My thoughts:
Any dead giveaways to tell if the alt is bad? Isn't it supposed to throw a CEL? This is my first "actual" problem with the X.
TIA!
My thoughts:
1. New battery isn't fully charged and hopefully it'll go up as she charges
2. Alt is dying and only partially charging. Low output killed the old/weak battery
I don't have the time to pull the alt and get it tested anytime this week. I plan on continueing to monitor battery voltage and hope it climbs back into the 13+ volt range it normally hung out at. Been a sweltering 90F or so for the past week with 60%+ humidity. So the AC was on a lot. Battery I replaced was of unknown age/brand. Looked rough and I had been intending to replace, but never got around to doing until today 2. Alt is dying and only partially charging. Low output killed the old/weak battery
Any dead giveaways to tell if the alt is bad? Isn't it supposed to throw a CEL? This is my first "actual" problem with the X.
TIA!
Posting Guru
Joined: Sep 2011
Posts: 1,287
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From: Fraser Valley
if you have a multimeter check what the alternator is actually putting out at the alternator stud. it should be charging at 13+ volts minimum. high 13 and low 14 is what you want to see otherwise its not fully charging.
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From: Central Coast of CA
Stewart
Senior User
Joined: Jun 2008
Posts: 108
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From: fort worth
AZ can check amp.output, wputs the charge into the batt. My diode was bad and volts were 13 but amps were only 30, not 130. Take your credit card with you. BTW,how old is it? Mine died at 190K mi. on my 2000X
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Senior User
Joined: Dec 2004
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From: sw mich
Fastest way, pull a battery cable while it's running. If it stays running, turn on headlights, radio, etc. If still stays running, try cleaning your battery cable.
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Fleet Mechanic
Joined: Sep 2002
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From: Greensboro, NC
No - not on a computer equipped vehicle! This can cause damage.
More Turbo
Joined: Dec 2006
Posts: 609
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From: Central Va
This would be news to me, we do it all the time in a number of different vehicles,
If the alternator is functioning, anything over 13v at idle is acceptable at idle with minimal accessories running. In this case, just shut all the ac and such down and just test at idle. If you disconnect the battery and it dies, your alternator or connections are shot. 90% of the passenger vehicles on the road are still just fine with the batteries disconnected, there are a few of the newer ones that will have issues, but none of them are the 10yr old excursions in question. We just spent the majority of the weekend under the hood of a '02 v-10 putting in dual alternators, and spent quite a bit of time with batteries disconnected and load testing the alts. No issues of course.
If the alternator is functioning, anything over 13v at idle is acceptable at idle with minimal accessories running. In this case, just shut all the ac and such down and just test at idle. If you disconnect the battery and it dies, your alternator or connections are shot. 90% of the passenger vehicles on the road are still just fine with the batteries disconnected, there are a few of the newer ones that will have issues, but none of them are the 10yr old excursions in question. We just spent the majority of the weekend under the hood of a '02 v-10 putting in dual alternators, and spent quite a bit of time with batteries disconnected and load testing the alts. No issues of course.
New User
Joined: Jun 2013
Posts: 15
Likes: 0
Sorry to jump in on this thread. I have a 83 F250 4x4 XL. 351W engine. I replaced the battery on Sunday and it started right up. I went to work on Monday without issue. This morning it started right up also. I stopped off to do something on the way to work and went to start it and it acted like it had no battery at all.
I put a charger on it and it barely made a sound. My coworker gave me a jump and it did not have enough juice to turn over the motor. It just clicked and made a "dead battery grinding sound".
Could it be the alternator? Did I ruin a brand new battery?
Rick
I put a charger on it and it barely made a sound. My coworker gave me a jump and it did not have enough juice to turn over the motor. It just clicked and made a "dead battery grinding sound".
Could it be the alternator? Did I ruin a brand new battery?
Rick
New User
Joined: Jun 2013
Posts: 15
Likes: 0
Before I tried to jump it, I got nothing. No click, nothing. After I hooked up the jumper cables I did get at least a click. I forgot to mention I changed out the solenoid last week. The starter is the next thing. Or the alternator is not charging the battery.
I put a charger on it and after work I will check it. If it does not turn over could it be the starter?
It is so frustrating.
Rick
I put a charger on it and after work I will check it. If it does not turn over could it be the starter?
It is so frustrating.
Rick