MAY NEW ALTERNATOR PUTS OUT 14 VOLTS WHEN I START THE DIESEL 5.9

amps or volts
11 to 12 amps indicates nothing but if it is volts then it indicates that the alternator is not charging the battery
Battery voltage is 12 -13.5 volts and when charging is 14.5-14.8 volts dc
the rest of your statement indicates that the alternator or voltage regulator is faulty and you should have the charging system checked by an accredited auto electrician

When it shuts off you will need to figure out if you are loosing spark to the plugs or fuel to the injectors.
Is the check engine light on when the engine is running ?

Take to an auto store and have them check the alternator, usually free, but sounds like alternator is on it last legs,

i would check the battery first. when the vehicle is not running the battery should have at least 11 volts, if not then the battery would be bad. when the vehicle is running, it should have at least 13.5 volts. a real good charging system would have close to 14 volts. if you do not find that the battery is bad and you are able to start your vehicle check the battery to see if it has the min. of 13.5 volts. if the voltage is dropping, then you have a bad alternator.

Hello
The normal charge of alternator on idling is about 13 to 14 volts. 12 is acceptable but keep in mind it will need attention soon. The needle fluctuates due to the revs of the alternator - there is nothing to worry about. Just look that the charge is always above 12V on idle.

you need to check your electrical system with a digital volt meter-when the vehicle sits overnight, the battery should read about 12.5 volts before startup. You should get the same (or very close) reading at the large post on the rear of the alternator, then start it up. Readings should go to close to 15 volts, and gradually drop down to close to 14 volts at idle, again at the battery and the rear of the alternator. If it is much less than 14 (like 13) or more than 15 (like 16) you have a problem either with the voltage regulator or the ecm.

first of all, check voltage at battery car off should read at least 12.5 to 13 volts. now start car. at battery it should read at least 14 volts, if lower then 14 volts check alternator.

It sounds like your alternator is not kicking in when the truck first starts. There is a wire that "tickles" the alternator to get it charging when you first start the truck, however it will start charging without that once you rev the engine up. A couple of good shots with the fuel pedal should snap the guage up to 14. If it climbs up slowly to 14 then the alternator is starting to wear out or you have poor contact.Get the alternator tested for output. If it's okay take the wires off the alternator and battery and clean up the ends so you have bare shiny metal and clamp them back down tight. Make sure you have radio codes and procedures before you unhook the battery. Hope this helps.

Check the alternator out put,with the headlights on,and ac on high blower motor,it should read,at the battery,13.65 volts,to 14.25 volts.

Your alternator is not putting out enough juice. Before you replace it, take a few minutes to make sure the belt is tightand clean up your contacts. Remove the wire ends, including battery cables, and clean them up with some emery cloth or fine sandpaper and reinstall. Your alternator grounds to the motor so don't forget to clean that too. Run the truck for 5 or 10 minutes to charge the battery a little an d see if that makes a difference. If it doesn't you need a new alternator.
If you have a multimeter you can test it yourself, the output should be at least 12.5 volts up to 13.5 or 14. Below 12 is insufficient. Hopw this helps.