Have replaced all battery wires cleaned anything that didn't even look dirty and am buying ac delco new not rebuilt alts voltage will swing from 11.8 to 14.3 and is never steady..

 

So the new one is toast no one has any idea?

 

So what are the symptoms of the alternators being bad?

 

It quits charging, test on vehicle or off no voltage..

 

You say you replaced all battery wires, but what about the battery itself?

 

Battery is good has been checked and a second good battery added just to have enough power to get home or nearest town to work on alternator, problems started before second battery added.
Took truck to the dealer and had connections to alternator checked and all connections were working as designed. So it is going back to dealership tomorrow morning. Also this is a 160 amp alternator that is factory option for this truck.

 

Is the truck stock? Any aftermarket subwoofers/amps?

What are the codes that are setting? Charging systems faults will set codes but may not turn on the cel.

 

No aftermarket junk.
No codes until failure of alternator
Dealership replaced gound current sensor and thought it was fixed but it is not. Mechanic says he has no idea if this doesn't fix it, he will have to call GM.

 

My first thought was maybe something is leaking into the alternator eating away at the windings over time causing short but where the alternator is located, I think that would be difficult.

Do you clean the engine compartment with any degreasers or other chemicals on a regular basis such as whenever you wash the outside?

My other thought is could a positive charging or battery cable be too close to the exhaust or other metal causing a short? I'd expect that to blow the mega fuse, however and I believe you mentioned the cables were replaced..

I think the ECM controls the alternator voltage in these. Has the ECM been replaced?

 

Not putting anything in or on my alternator. Yeah all of the cables were checked, most replaced. Batteries are good. Yes the computer controls the alternator but which one? And how do you know if it needs replacement or reprogramming?