Good way to diagnose fans is to start car and turn the A/C on which will force or command the fans on no matter what, you wont have to wait for the car to overheat. If they turn on then the circuitry fuse etc are fine and your overheating issue is elsewhere. Do this first then go from there. At this point you can disconnect the connector for the fan and load test the circuit. Fans rarely go out, in heavy load situations like this relays go bad left and right so start checking fuses and relays, then if alls ok, load test the actual connector at the fan.
I'm having a similar problem I think. My fan does work but it's not kicking in until my engine is really hot then it turns on. It works under most conditions. This happens when I'm idling, if I idle for a long time the engine gets hot and then fan doesn't kick in until it's in the red part of the temp. gauge. Could this be because of a faulty CHT sensor? I'm need some advice ! Is this just normal? Thanks!