Battery Draining?

[NC-Expy]

I have no issues when the truck is running and moving, the battery tested good and the alternator tested good. They are both brand new.

When the engine is on but not running, the voltage gets really low and the battery begins to drain about 10 minutes in. If I don't crank the truck right away the battery will completely drain and not start.

Any ideas? I know the connections/grounds are good.

 

[ELVATO]

Kinnda confused by the second part. Do you mean with the key in the ON position, but the engine not running? Or do you mean when idling? I'm thinking the first one cuz you mention cranking later.

Does it doe it if you just leave the key in ACC, but not in the ON position?

 

[NC-Expy]

Kinnda confused by the second part. Do you mean with the key in the ON position, but the engine not running? Or do you mean when idling? I'm thinking the first one cuz you mention cranking later.

Does it doe it if you just leave the key in ACC, but not in the ON position?

Sorry lol I figured that would sound confusing. The battery is draining with the key in the ON position without the engine running, when the engine is RUNNING, the battery does not drain at all and holds it's charge perfectly.
When the battery is on ACC, there are no issues.

 

[toms89]

Not sure why you would leave the key in the run or on position with out starting it but anyways....

Can you verify the fuel pump shuts off after a few seconds when key is first turned to the run position? Is your heating and air turned off? Even on the lowest speed setting the fan is running.