Alternator?
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Joined: May 2007
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Alternator?
Every once and awile (about every 3-4 weeks) my battery dies randomly.
I have not been able to establish any kind of a pattern to the draining.
Yesterday, I got stuck in traffic for 1 hour and 1/2 and my batteries went dead with the truck running..
I did some testing when I got home. Once I sort of charged the battery, I started the truck and disconnected the alternator. I tested the batteries and they read 11 volts (still not fully charged, I only charged for 1/2 hour)
Then I tested the alternator output, it was 2 volts.
So right away I thought dead alternator, right? Wrong. When I reconnected the alternator, It started putting out 12.5 volts. I believe the voltage was low(12.5v) because of the low voltage on the batteries.
So I've got a couple of questions for you guys
Has anyone seen an alternator work, then not work, then work again?
What other testing can I do?
Does the alternator only put out a charging voltage when it is connected?
Am I missing Something?
PS- the batteries are only 1 year old and seem to take a charge just fine.
I have not been able to establish any kind of a pattern to the draining.
Yesterday, I got stuck in traffic for 1 hour and 1/2 and my batteries went dead with the truck running..
I did some testing when I got home. Once I sort of charged the battery, I started the truck and disconnected the alternator. I tested the batteries and they read 11 volts (still not fully charged, I only charged for 1/2 hour)
Then I tested the alternator output, it was 2 volts.
So right away I thought dead alternator, right? Wrong. When I reconnected the alternator, It started putting out 12.5 volts. I believe the voltage was low(12.5v) because of the low voltage on the batteries.
So I've got a couple of questions for you guys
Has anyone seen an alternator work, then not work, then work again?
What other testing can I do?
Does the alternator only put out a charging voltage when it is connected?
Am I missing Something?
PS- the batteries are only 1 year old and seem to take a charge just fine.
Posting Guru
Joined: Aug 2008
Posts: 1,845
Likes: 1
From: No.Va.
Begin w/ fully charged batteries.
Check voltage w/ engine off. This will be battery voltage.
Start truck wait a minute or 2,check voltage again,this will be running voltage.
If your alternator is good,it will be appx 13.5-14 volts.
Turn on hi beams,a/c,high blower motor etc.,read voltage again.
From your 12.5 v running,alternator is suspect for sure.
Check voltage w/ engine off. This will be battery voltage.
Start truck wait a minute or 2,check voltage again,this will be running voltage.
If your alternator is good,it will be appx 13.5-14 volts.
Turn on hi beams,a/c,high blower motor etc.,read voltage again.
From your 12.5 v running,alternator is suspect for sure.
