Thermo fans

Yep series/ parallel relay setups were the norm for early brush-type 12vdc fans. not a lot different from the hvac cage fans in the rrc - except that uses a multistage resistor made from nichrome wire (as many manufacturers did at the time).

There are plenty of PWM controllers on the market and many take multiple fans, but not many are designed for high current brushless dc motors. Most modern vehicles control the pwm signal from the canbus, which means no standalone module like the falcon example.

There are also electric water pumps, and auxillary water pumps which can boost circulation of the coolant at low engine rpm when the coolant temperatures are elevated - these work well in conjunction with electric fans, but as I stated previously, there is a significant penalty in current consumption at low engine rpm, so the alternator and battery capacity has to be upgraded to reflect these demands.

It's not enough to simply drop in a semi-constant high-current demand circuit without giving consideration to the load placed on a standard charge/storage system.

Personally, I would not risk using a standard single RRC battery and alternator setup if I was dropping in twin electric thermofans. It's just like upgrading your H4 globes from the standard 55w units to a pair of 130/90's and adding a pair of 100w H1 driving lights to the high beam circuit.

Something has to give, and it's almost always the battery and alternator not able to keep up with the high current demands due to the increased consumption.

Just as an example, the twin 16" spal pwm fans in my RRC consume 25A each at 95% duty cycle, 30A each at full noise. That is a soft ramp-up from approx 5A to 50A if the temp sender in the thermostat housing detects the coolant temp at 105ºC for more than 30s.
At normal operating temperatures - between 90-100ºC, the fan speeds are controlled by the natural hysteris loop and the pwm controls the speed using a log curve.
Under load, up long steep grades (>8%) that we have an abundance of here, the current demand typically doesn't exceed about 16A in normal highway driving conditions up steep grades.
It was no different when I lived in nsw, e.g. bulli pass was never an issue - or Moonbi... no problems.

All of the FNQ tablelands climbs present no issue, with no excessive demands, unless towing a 2-ton load. That does work the cooling system hard, and the thermofans cope extremely well, keeping the engine at a solid 95 degrees under sustained 2nd gear / 3rd gear full throttle demands of the climbs.
What that provides is a natural reassurance and the ability to focus on driving rather than keeping the attention focused on the temperature gauge.

One further safety incorporation is the use of the temp trigger in the Redarc temp gauge - which provides a full-power override to the PWM controller, when the temperature reaches 110ºC. When this occurs, the temperature is pulled back down to about 95ºC in under a minute. That's under sustained high rpm low speed (relatively) hillclimbing towing a load.

The same setup could easily be achieved with two different thermoswitches or a duplex thermoswitch. one for low speed and one for high speed - and this would be just as effective. The trick is to know the exact temperature that you want the coolant to reach before the high speed fan setting kicks in.

Ultimately, the KISS principle is paramount. Install the setup that you are most comfortable with, one you can diagnose all the failure modes and repair on the side of the track if you get stuck. Whether that's a viscous coupling fan or electric fan, the ability to effect a repair in the event of unexpected failure is what counts - before you cause any engine damage.