Okay heres the situation.
2004 Expedition 5.4L Non nav system

Drove the truck to the store and back about a 20 minutes drive, get home and smell something burning. Pop the hood and theres smoke coming out of the alternator so i'm like shoot. I disconnect the battery just to be safe and let the truck sit. I go back the next day and reconnect and fire the truck up, and sure enough, the battery light is on and it says check charging system. Check voltage at the battery while running and its approx. 11 volts (not charging)
So I remove the alternator and take it to the guy to have it rebuilt (cuz there 200$ NEW-screw that!)
He takes it, hooks it up to a system he has, which spins it, loads it and checks output. It works perfectly! Even under total load, its outputting 110amps and putting out 14 volts. We let it run for a few minutes and it still is performing perfectly under load and all. He then switched it and checked the diodes and those checked out fine.

First concern: The thing was smoking/ smelled like burning plastic.

Second concern: Smoke aside, if it is okay, then I popped one of the fuses either the one inside the truck of the MEGA fuse under the hook, havent checked those yet, BUT if one of those is blown, What would cause it to just blow? Is this common? Also did a amp draw test just to see if there was a huge draw when the truck wasnt running and it seemed pretty minimal to me (barely arched).

Any suggestions guys would be great because at this point I'm about to just replace fuses and have it rebuilt.

*Connections we NOT corroded / NOT melted, everything looked good. NO melted wires or nothing out of the ordinary.

 

It doesn't matter that it tested good, smoke coming out of it is a sign that it's no good. Personally, I wouldn't waste the time or money to have it rebuilt, I would replace it. You have no idea what damage there could've been to the windings.

 

When they rebuild them, dont they normally redo the windings too?
Also i just checked and he MEGA fuse running from the alternator to the battery is GOOD. :/


$200 for a new vs a fraction for rebuilt idk. trying to weigh out my options, its only my winter vehicle

 

Nope, most rebuild shops just replace what's worn, like bearings, brushes, any blown diodes, etc.

Some shops simply test them and if they test good, clean them up, box 'em, and ship 'em out.

 

If your alternator tested fine than it must be. I would start checking the wires from alternator to the battery and elsewhere. Something probably shorted to ground and fried the wiresor pig tail. Start by doing that. If your alternator was junk, well, it wouldn't have tested good.

 

I had the same burn smell on my 03 along with the check charge system light. The alt smelled burnt and there was burn residue (don't know how else to describe it) on the engine behind the alt. I ended up having to replace the alt and battery. Don't know which one died first, but I figured the death of one caused the death of the other. It's been almost 2 years and everything is fine. FYI, I replaced the alt with a unit from Autozone.

 

And you're basing this information on what, a guess? All too many here and elsewhere eventually solved similar issues by replacing alternators that had tested good.

 

Once again, here you go! That was a reference to what the shop was telling him and most likely it is fine. Yes, the alternator can still be bad. I have seen it more times than not the alternator is good but something else caused the problem. Sorry, I forgot that you know all so I will make sure I click on you reputation points to boast your ego some more. Nothing like making sfedenis spend a few bills and have it be wrong.
If you can sfedenis, put the alternator back in if you haven't done so, and take your truck to a shop and have them test the charging system. It will check most everything in the charging system. It may point to an issue elsewhere. Then if the alternator is bad when they test it, you know for sure and you shouldn't have to worry about spending the money and have it not be your problem. If it is the alternator, then I would have a talk with the place that tested it and ask them how that happened. Good Luck. Keep us informed!