Ed does your truck have a glove box light?If so take the bulb out.Then check,maybe the light is on when the door is closed.My Father-in-law bought a used car that always drained the battery.
as I disconnected the ground to start testing he heard a click.Trying to follow the sound we found a relay,traced the wires.It was connected to a hidden toggle under the dash,which was turned on.Disconnected the curcuit to the switch:Trouble was gone.We never did know what the relay was for.[not a factory install]
