Medium on all the time when ignition is on.

ECU still able to go to "HIGH" when the temps call for it AND still have the fans run after the ignition is off, if the thermoswitch sees temps higher than the PFC's set amount?

 

My understanding is that the fan recall box will keep the fans running if a preset temperature has been met during operation. I think that this temperature is embedded into the firmware of the box and has nothing to do with the PFC. You could probably do some trickery with resistors to fool it into seeing a higher temperature than reality to trigger it at a lower temperature.

 

I think you should get the results you're looking for by wiring the control signals for relays 1 and 3 to ground, and letting the ECU control relays 2 and 4. It might be a bit of a pain to wire.


That said, I don't necessarily agree with your idea. I suspect the thermostat will be closed more often than not and that will restrict coolant flow. Don't forget that the thermostat has a bypass valve and can prevent coolant from entering the radiator if the engine is "too cold."

 

IIRC, I've read posts where continuous fan running wears the fan motors out in a short time. So, IMO, that's not a good idea.