Need help ASAP, truck is dead!

Farmer Rock

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I pulled into work this morning and I noticed the voltage started to drop again, just like it did before I replaced the batteries.
Something drained the batteries and it wouldn't restart, started to act like an alternator gone bad. Got a new one at Napa and had the brand new batteries load tested while I was there.
I think the new alternator is bad, only reads 3v on the big lug without the cable on it...........
I can't get exchange it till the morning.
I got really behind on my work because I needed my truck, and it's still sitting there.
I traced wires,cables, tested fuses and circuits. No red flags.
Batteries are drained to 11.5, but it starts right up with a jump and runs great. Trouble is, after a few minutes I can just sit and watch the voltage gauge drop until it gets to 9v and the gauges quit, wipers go crazy, then engine dies at around 7v.
I'm gonna swap the alternator in the morning, but I was wondering if there's anything I might be missing.
This doesn't strike me as a dead short, because the voltage consistently drops until it died.
I could really use some help here, these motors are new to me.
I would appreciate any and all help.
Thank you

Rock
 

Farmer Rock

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one thing to check is the pigtail on the alt, i have seen more than one not making contact and not turning the alt on, other far off posibility is something is telling the glow plugs to turn on.
It sounds like the glow plugs keep clicking on and off awhile, but I'm still getting used to this.
What's the best way to disconnect the GPS to be sure?
Thanks
 

Farmer Rock

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Do you guys think they just gave me a bad alternator then? I'm just wondering if there's anything I might be missing.
Thanks
 

TNBrett

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You can check and make sure the glow plugs aren’t staying on. It’s completely plausible that the contacts are welded in the relay. Otherwise I’d have the alternator tested. Oh, and do a thorough check for battery cables etc. shorted to ground. It sounds like a pretty serious draw on the electrical system.
 

Farmer Rock

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Got the alternator tested, it came back good. I got it swapped out anyway. Does the same thing.
I put the batteries on charge, and am starting to thinking the batteries and alternator have been playing games on each other.
Here's what I'm thinking...
I put new batteries in, then the alternator goes out and of course causes the batteries to get drained. Then I swap the alternator, jump start it, assuming the alternator would pick up the slack on the low batteries but it doesn't.
Does this seem right?
I just get the feeling I'm fighting the same stupid stuff over and over.
I'm hoping after the batteries finish charging up, it will hold voltage. We shall see.
Thank you guys for the insight!


Rock
 

aggiediesel01

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Have you tested the regulator or at least checked the plug there? Your regulator is external to the alt unless you have converted to the 3G alternator.
Disconnect the heavy wire going to the GP controller to see if that eliminates your current draw. If it does, then your GP controller is bad.
 

Farmer Rock

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Have you tested the regulator or at least checked the plug there? Your regulator is external to the alt unless you have converted to the 3G alternator.
Disconnect the heavy wire going to the GP controller to see if that eliminates your current draw. If it does, then your GP controller is bad.
All I tested was the big lug on the back of the alternator. I didn't realize the regulator was external. Can you please explain how I should test it? This is a first working on a PSD for me. Thanks


Rock
 

aggiediesel01

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Nvrmnd, I didn't notice what forum I was in, I thought it was the truck in your sig.
You have the 3G in a powerstroke w/ an internal regulator. I would suspect the GP controller first. Disconnect it and see if the drain goes away.
 

aggiediesel01

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Ok, it’s an e99. I think you have a hot air intake heater as well in the intake y pipe. Disconnect that as well to see if the drain goes away.
 

aggiediesel01

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Go on eBay and get one of the Ford Service manual CDs that covers your year. It will have all the diagnostic/troubleshooting plans as well as all the wiring diagrams for the entire truck.
 
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