On a 1997 Ford Thunderbird LX 4.6, what would cause the cooling fans to run when you first turn the key to the "on" position?

Usually, the module controlling the fan(s) will turn them on when there is a malfunction. It's engineered to do that to prevent engine overheat when the module can't operate the fans properly. The control module, PCM, ECT or wiring has a problem. It will reqiure a scan tool that can read PIDs to see what has failed.

The issue turned out to be the PCM. It, for whatever reason, was not booting up and able to perform engine control functions. The PCM has to send the CCRM a signal to turn OFF the fan. There also was no communication to the PCM by way of the OBDII connector with a code scanner until the MIL blinked. See the other post under 1997 Thunderbird that would crank but not start until the fan stopped running.