A slight twist on the adjustable Davies-Craig thermo switch.
I had a small copper tube soldered into the top radiator tank, with the inner end sealed off.
I slipped the sensor bulb into the tube, snug fit.
Then adjusted the thermo-switch to operate the fan relay when the in-car mechanical temperature gauge reached 95deg.C.
[This was with an 85deg.C. thermostat.]
I have it wired so that the fan relay always has power.
That way the fan will run after engine shutdown to prevent heat soak.
The advantage of this arrangement is that you can adjust the fan to operate at any temperature you desire, within the range of the thermo-switch
Has been 100% reliable and maintenance free