+1 on this, a clamp on ammeter works well also.

 

I had a chrysler car that this was happening on. it kept killing my battery to the point it ruined it. it turned out to be that the battery terminal clamps were corroded. You wouldn't have thought so by the look, but i took the clamps loose and cleaned them with club soda, and put them back and the car fired right up. So i took them loose again and put terminal grease on them and the battery hasn't died since. You might try it, never hurts to go for the simple solution first.

 

I had a similar issue, my alt wire under the positive clamp was loose so my battery wouldn't charge right. Not so much the same issue as OP but I cleaned all cooper connection dielectric greased and tightened and I get a full 14v now unlike before I was only at 12.6, 13 when driving.

OP after you find if something is pulling a draw while engine is off, freshen all connections and put grease on em and they'll last forever. Good luck

 

start the truck and while running pull the positive cable off the battery if it dies ya alt is crap if it stays running something else is draining the battery maybe start is drawing current or another bad connection

 

I wouldn't recommend this. There is a chance of frying something, more specifically, the computer. These newer cars with high voltage ignitions and computer controlled everythings are a bit finicky when it comes to voltage spikes. Disconnecting the battery when the engine is running gives the Alt no where to send the voltage that it generates when it is spinning. More often that not, you will get lucky and nothing will happen if you do this, but the risk you take is not worth it. I wouldn't do something just for the sake of troubleshooting if there is a chance of damaging something as important as the computer.

 

Well I put the test light to the + and the test light is on. I remove all fuses one by one and the light didnt went off. Anyone have any suggestion??

 

Do you have a fuse/relay box in the engine compartment? I have one in WJ but I have the 4.0L. i am not familiar with the 5.2Ls. You may want to pull the relays as well.

 

Also disconnected the altenator and the light still on don't know what to do next

 

I check all fuses under hood and in passenger side

 

Did you ever fix your issue

 

No I'm still looking to see whats the problem. So far is the #7 fuse and also the cruise control under the hood staying on so I unplug it

 

Do you have the button on your steering wheel for your cruise control?

 

Yes I do but I unplug them and still the same

 

Have you checked under the steering column to make sure no wires melted together or anything there is constant power under there. Just wanna make sure nothing got crossed.

 

When doing the fuse test did you pull the off-draw fuse too. If you did not you will get a light. The off-draw fuse is always powered. It is used to power things that you may need with the ignition off. Radio memory, lights, etc. Not sure all that it powers have not checked schematic.