dodge 3500 cummins clutch fan engages on flat with no load

correct me if I'm wrong, NV5600 has a small external cooler as does the engine oil. I have not seen any cooling lines going in the rad.

I do not understand OATS and HOATS, I flushed out all the coolant several times and I am running plain water for a few days until i work this out.

This weekend I will conect the hose flush thingy, remove the thermostat (or take my old on and lock it open) and flush it until i can drink it.