Did you add any accessories recently like a after market modern radio/CD/cassette player.
If you did go to this Post
Modern radio/CD/cassette players do not shut off completely when you power it
off from the main radio/CD/cassette players on/off switch/button.
If you do not remove power from accessories switch wire the unit will continue to draw power.
If you have not added any accessories recently disregard this post.

Thanks,

1954 Chevrolet 3105 Deluxe Panel Truck
w/Factory HYDRA-MATIC