Temperature Switch or Thermistor?

That's the chts, cylinder head temp sensor and it is used by the ecm for fueling calcs. So no its not a switch and no u can't use it for efans

Thank you … I guess that settles that.

There is however a switch in the rad that is for the ac fan, it I think closes at 212deg.

Buy a hayden fan controller module. Has temp probe and everything you need to run a dual fan set up

The thing is, I have a Nissan 2-row aluminum Euro radiator (its core is aluminum, the frame and top/bottom collectors are black composite). It bolts up pretty much as the US OEM unit and very easily adapts the fan shroud. I bought it when I needed a new one, and since I was adding some HP and this was designed for Euro cars, which had more power, I went with it. Anyway, at the base came 2 thermo switches, so I decided to use one as my e-fan switch. Trouble is, when I run the engine, no matter how hot the coolant gets (gauge needle at 75% full scale), the e-fan never comes on. I tried both thermo switches --- I dared not to let the coolant get any hotter than 75% of full scale. Unplugging the switch and simply using a paper clip as a jumper, the fan comes on and the coolant quickly gets down to normal. So it's not the fan, relay or circuit --- it's those damn thermo switches. (Nissan makes their radiator thermo sensors such that you can't swap them with any aftermarket unit, as the threads are straight machine threads, not pipe threads as most US aftermarket sensors are. They seal with a rubber O-ring.) I'm also using an EWP, so the radiator body is getting quite hot, as are the sensors. I feel having a sensor right at the base of the radiator is actually a good place to take readings, since if the coolant isn't being cooled enough without the fan, it then comes on as needed. But finding a working sensor that will fit the radiator, and close at say 185 degrees, is not that easy.

The hayden kit comes with a sensing probe and a dial. You install the probe through the fins near the coolant inlet then adjust the dial to have the fan kick on when you want it to. Some kits come with a built in circuit to run a 2nd fan when the temp reaches 10° above where you set it. Also comes with a wire to activate one fan when your ac clutch is turned on.

Thank you.

I looked into the Hayden units and found one that uses a threaded sensor, which got me thinking … perhaps I could find an adaptor/collar that this could thread into which could then thread into the radiator's thread. Might you happen to know the thread size/pitch at the base of a Z31 radiator. It's the same as in my Euro radiator. (M12? M16?)

dont install it in the lower corner of the rad where that switch is, not an accurate reading point, as it's very out of the path of normal flow. Derale has a better lifespan/less failure rate than Hayden. I'd look into a threaded sensor, and put it in the lower intake manifold.

That's a good suggestion, but where exactly? It seems all the threaded holes in the manifold are already taken. Also, what is the desired temperature of coolant leaving the engine (pre-radiator)? I ask because if I can't fit one in the manifold, I can use a hose connector with a tapped opening made for a thermal switch (or simply tap it to fit). I can locate it between the outlet from the engine prior to the radiator.

You want the engine operating 190 -200° F
there is a plug threaded in the driver side of the LIM that you could probably use.
Honestly it depends what your thermostat starts to open at. If you have a 170° Tstat it's full open at 190°. So you want to make sure that your fans don't cool your coolant below 190 because it will cause the thermostat to continually open and close. Leading to short thermostat life span.

Well, I peeked in there and found one threaded fitting on the front half of the manifold (driver's side) --- but there's a sensor already in it. It has a single black wire coming out from the top center.
As for my thermostat --- I'm not using one. I have an EWP that is PWM speed controlled by measuring the outlet coolant temperature; the sensor is bolted to one of the two bolts holding the radiator cap housing, so it pretty much is at outlet temperature. It can also be calibrated to adjust the speed at different temperatures, making the engine run warmer or cooler. The set up actually works really well, if I manually turn the e-fan on and off manually, bypassing the coolant temperature switch. The temperature gauge in the car reads as it did before the mod. All I really need is a good fan switch at the right setting and I'm home free.

Ok I see. So that sensor on the driver side LIM your seeing is part of the oem condenser fan switch (I believe) mine is just a plug with nothing on it lol.

What exactly do you mean by "condenser fan switch"? The A/C condenser? If so, that should be on all cars that have A/C … which is every car (from the factory).
So what else could you mean?
PS: I gutted all my A/C components years ago --- no compressor, condenser, front fan, etc.