That system should be run by a basic coolant temp sensor for the ECM.
There CAN also be a coolant temp sensor/switch that runs the instrument panel cluster TEMP gauge/light, too.When the coolant gets to a certain temp, the internal switch closes, and the ECM commands the fan to run. Might be a relay in that circuit, too? Reverse happens when the engine stops.
Find a wiring schematic and trace the electric circuit for the engine cooling fan. There is quite an online following for the Chrysler K-car and Extended K-car vehicles. Used to be a Yahoo Group on "Shelby Dodges and Turbo Chryslers" (or similar), which might have morphed into another online group.
Just some thoughts,
CBODY67