Battery Light on
Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
Then you really have no way of knowing what is wrong.
When you accelerate, the truck uses more power (e.g. FICM) and less when you are at idle.
Do a proper alternator test --- eg measure voltages at the battery sense and light wires... and also do proper measure of output via clamp on ammeter and volt meter.
Thread Starter
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New User
Joined: Feb 2010
Posts: 18
Likes: 0
Went out & tried to start this morning & it barely turned over so something drianed the batteries overnight. I haven't had time to get the alternator off, it will probably be tomorrow before that happens.
Hotshot
Joined: Jul 2005
Posts: 13,834
Likes: 25
From: Middle Tn.
A bad diode in the alternator can drain the batteries over night. I think this may be telling you something.
Hotshot
Joined: Jul 2005
Posts: 13,834
Likes: 25
From: Middle Tn.
Read the other replies of people that have gotten bad rebuilt alternators. Some that took 3 or 4 to get a good one. Rebuilt means what the rebuilder thinks is bad gets replaced, nothing else. Diodes can be self healing and show up good after cooling down and after heating up fail again.
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Senior User
Joined: Sep 2004
Posts: 329
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From: Carroll County, MD
Read the other replies of people that have gotten bad rebuilt alternators. Some that took 3 or 4 to get a good one. Rebuilt means what the rebuilder thinks is bad gets replaced, nothing else. Diodes can be self healing and show up good after cooling down and after heating up fail again.
Been There - Done That with respect to bad alternator rebuilds. Furthermore, seldom (if ever) is a rebuild tested in under-hood conditions, like vibration and 200 degree air blowing across it. I had nothing but bad luck with rebuilds, but have had great luck with the Advance Auto alternator, because it was NEW, not reman. Hence all new parts.
EDIT: It was a little more expensive, but worth it, as it also has a lifetime warranty. Not saying I have not seen the problem with the pigtail as well. BUT, with something killing the battery, and the only thing that has changed is the alternator, well.......
Posting Guru
Joined: Jan 2009
Posts: 1,328
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i think the only thing that drained your batts was the fact your alt wasnt charging them when it would run.it could very well be a pigtail issue too.
Post Fiend
Joined: Jul 2005
Posts: 6,127
Likes: 6
Read the other replies of people that have gotten bad rebuilt alternators. Some that took 3 or 4 to get a good one. Rebuilt means what the rebuilder thinks is bad gets replaced, nothing else. Diodes can be self healing and show up good after cooling down and after heating up fail again.
Quality rebuilders test the components at operating temperature and conditions.
But if you buy a "no name" rebuilder --- you are on your own.
I went with a custom rebuilder --- one that I can march back to and complain if the thing failed.
New User
Joined: Jul 2011
Posts: 1
Likes: 0
FIX?
Did you ever come up with a fix for this? I'm having the same issue.