In case this is not common knowledge yet, let me share a couple of things I learned from tracking radiator and condenser in and out temperature.
1. Engine heat seems to reach radiator with time delay. Temperature goes up faster at traffic stop right after highway cruise than stop and go city traffic.
2. AC generates heat much more than I imagined. Now I understand members experiencing little to no cooling at idle.

 

That is why I don't like using the probe style thermal switches. Too many factors involved.

 

What do you recommend?

 

Same one I did in your last thread. The BMW sensor. It's an all in one 2 speed sensor. Don't have the part number handy right now, but I can get it.

 

Here is the switch 61311378073. The plug in wire socket is 61131378410.

 

The merit of the dual thermostatic switch is no external control is needed. Do it once and forget. It's still a good option.

If I may add to this setup based on my observation with my 97 4.2L 2" thick radiator, fan control from radiator outlet temperature probe,

Thermostat constantly opened and closed, cycling coolant temperature between 189 and 201 (195 set plus minus 6) whether air temp was 30 or 80. Fan came on occasionally at traffic stop. A thermostatic switch would constantly cycle thru activation/deactivation at all vehicle speeds.

Running AC didn't change thermostat cycling, but raised vehicle speed for adequate natural cooling from appx 20 to 40 mph. Fan kicks at most stops and stays on until appx 40 mph.

Highest air temp so far has been lower 80's. I have yet to see what happens in Florida summer.

 

No external control needed? Explain.

 

The BMW switch does the control with the help of Volvo relays. But I have to monitor radiator outlet temperature with Arduino and Arduino compatible relays. I don't have the confidence in my setup yet to recommend to others.