As I recall, the coolant temp sensor sends a signal to the ECM, the ECM then uses this info to operate the fan relays. If these units are original, you might expect to replace them. Look for voltage and ground on the appropriate wiring, at the time when you would expect to see the fans run. If the ground is missing, repair this; if the voltage is missing, more troubleshooting is necessary. You could also try bypassing the control circuits and apply voltage to the hot terminal; if the fan does not run, it is the issue. One caveat... the motor will draw a lot of current on start up. Expect to need wire larger than 14 gauge, something like 12. Ray