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Discussion Starter #1 (Edited)
Truck ran great, until this morning. I started it fine, no slow crank or anything, let it warm up for 5-10 minutes and left for work. First thing I noticed was my headlights looked really yellow/dim, then noticed my airbag light was on. I pulled out of the drive and then noticed the instrument cluster lights looked dim and then the gauges stopped working (500ft from driveway). Decided it wasn't a good idea to try and drive to work, and I'm glad I did. On the way back home (1500ft) my CS turned off while I was trying to see what the battery voltage was (I didn't see it before it shut off). I got it back to the driveway and shut it down, and started the other diesel to make it to work. Before I left I saw the CS was still on??? I tried to start it before I left for work in the car, and the batts are completely dead (brand new MC batts)

I did not get a low battery light, just the airbag light. The truck ran for at least 1.5 hours last night after getting it running with no issues in the charging system, no airbag light and no dim dash lights

FYI, I lifted the cab

@toren302 @kaya @Lilpooh @LoxDiesel
 

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I'm definitely banking on a loose connection. New problem after doing some major work, no doubt that's whats going on. Back track every connection, you'll find it.

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That's what I'm thinking. It's just weird that it ran as long as it did last night, and this morning, this
 

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That's what I'm thinking. It's just weird that it ran as long as it did last night, and this morning, this
Well if those were brand new batteries, it probably would run fine for awhile until it didnt have enough juice to operate the ficm. I had my alternator go out last year and it did almost the identical thing. Instruments went out, airbag light came on, the works. I wouldn't stress too much. Once you find the culprit you'll probably do what I do when i make a rookie mistake and say" I'm an idiot" seems at least every repair I find myself saying that to myself.

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You never had a low battery light come on? I have two alternators to check now, and hope that my batteries come back. They're under warranty though :D
 

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You never had a low battery light come on? I have two alternators to check now, and hope that my batteries come back. They're under warranty though :D
Never saw a low batt light until it died.

Let me make sure I'm hearing this right. You have two alternators to check on NOW, as in you installed a second one recently?

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Discussion Starter #7
No, I just mean that I will have to remove them both to be sure they're both ok. Came from the factory with two :thumb:

The way this job went, it wouldn't surprise me that i have one, maybe two bad alternators :ranton:
 

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When my alternator went out I didn’t get a low battery/charge light. Driving home during daylight, gage cluster needles all dropped to the left and luckily i had my SCT X4 on and looked and seen Battery at 3.6v. Checked was getting power to the alternator but wasn’t getting anything coming out of it. Threw the batteries (a month or two old) on charge while I ran up to the parts store and grabbed a new one. Got home, installed it and she fired right up. Mine is an 04 so maybe they don’t throw a code or are supposed to and my didn’t.

To check the alternator is free and if that’s not it then like everyone else said I would say you got a wire touching somewhere. I wish I had dual alternators.
 

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Discussion Starter #10
That's what mine did, Ryan, among the other things I mentioned. I did read that I could have had one bad alternator and that kept it going, but now that one may have failed also. Yippee, I get to buy TWO of them, haha. Oh well, could be worse!
 

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Discussion Starter #13
true
it is common to have a bad alt on duals and not know it until the other takes a dump

but it is still suspicious that you just got done wrenching
To me the alt was fine last night for about 2 hours while I was running and test driving the truck without issue. I wonder if sitting for over a month and then getting that one last heat sink to it gave up the ghost :dunno:

with dual alts maybe the PCM was flipping to the good alternator :dunno:
It shouldn't take that long IMHO. I will have better info for this thread tonight when I can dig into it a little bit. More to come
 

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Discussion Starter #14
Update:

The truck is running/charging great now. I found one connector for the lower alt not connected. I also replaced both alts. The lower one was only charging at 9.5v and he upper had some squeaky bearings, but charged great. I also learned from @a2elvis that you need to wait about 30 seconds before the alts start charging! Thanks for everyone's help!
 
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Update:

The truck is running/charging great now. I found one connector for the lower alt not connected. I also replaced both alts. The lower one was only charging at 9.5v and he upper had some squeaky bearings, but charged great. I also learned from @a2elvis that you need to wait about 30 seconds before the alts start charging! Thanks for everyone's help!
Stoked to hear all worked out! Enjoy the drive!
 
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