alt or battery
 

At idle my truck wont charge and it wont under 1500 rpm wont charge when I have it higher it takes about five to ten seconds to get up to almost normal charging power at the end of the r. Then I let off and it slowly drops. It use to have hard tome charging at idle but even 100 more rpms. And it would jump to normal charge. It starts strong and fast even in morning? Could it be dead battery still giving it a draw or just bad alternator?

I don't see a problem here. What are you going by to know if it is charging or not? There is no reason to charge fully charged batteries. Remember that the glow plugs will continue there draw until the engine is warm.

Ya glow plugs shut off after like 90 seconds . My volt gauge shows its not giving a 14 volt charge unless hi rpm other then that it is 12.5 wich is no charge

were does the battery meter go once it starts to drop???

test the alternator...

I was at work just was wondering if it could of been a dead battery putting. A draw on the system, witch would of caused it to only charge at higher rpm it was the altrntor

its probably the alternator

Agreed, test it