you can put your meter or test light from the disconnected + cable to the battery pos post and see if there's actually a current flow with everything turned off - also disconnect the battery to see if it will take a charge by itself, isolated from any wiring, might be a bad cell

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics