Dean, the electric fans are controlled by both A/C circuit and temperature sensor. So they should come on on their own, and in my experience it was about 230F.
I am tempting my fate right how -
maybe my D1's temp gauge is stuck in the middle, but - it has never gone past this mark, on the highway (say, I70 towards Eisenhower tunnel at 55mph in the 2nd gear at 100F outside), or in sand pulling a Grand Cherokee, or in any other situation. Never tried mud, however.
Took me 4 years to not having to pop the hood on the jeep, though.