1986 Mazda 323 resistance of good coolant temp gauge sendin

Which component are you working on-Is it the coolant temperature sensor or the engine temperature gauge sending unit? If its the CTS go here:

https://www.2carpros.com/topics/cooling-system/coolant-temperature-sensor--2

Am presently working on the sending unit for the dash mounted analog water temperature gauge.

I am hoping that if I get to a place where I have a more accurately reading one that that will help me to see if the radiator mounted electric fan is coming on late or intermittently.

The usual parts sellers show a 3 parts that have the designation of ~ "cooling" or "coolant" with words like "sensor" or "switch".

But the one electric wire off the top of the thermostat housing has a single flat male blade or spade lug. (( 3 different parts places show a single connector with a sort of rounded "pin" that has a sloped portion at the end.))
Also is a single flat blade located at the driver's side end, not so far from the top of the engine block & is on the side of the engine block facing the radiator that has a single mating wire for it.

I think there is another sensor that is in the real top suface of the engine that has 2 side by side flat blades that is for the ECU.
I measured its ohms at 130 & 160 degree F & it stayed at 41 ohms. Since I think that this is the sensor that feeds analog temp info to the ECU, I think that it must be defective


But am thinking that the sensor that interfaces with the dash mounted water temperture gauge is for the driver's use only & does not interface with the electronics of the engine control system.

The exact function of the water temp sensor (2 prongs - not flat) in the bottom, driver side of the radiator has various answers depending on various sources. It seems to be involved with turning the radiator's electric fan on - but some say it works in conjunction with the single wire sensor mounted on top of the thermostat housing.
I measured the 2 prongs ohms after the car had cooled for a while & it was same as when warmer, namely, zero ohms (but the fan was not on at either water temperature).
Also I get varied info as to exactly what temperature the fan is supposed to start operation.
(this car is "basic" - no air conditioning, etc.)
If the thermostat is supposed to be 180 or 192, then one would think that the fan should come on not too great of a temperture above that but of course if its control is via the 2 prong sensor in the bottom of the radiator, then the sensed temperature will be ?? 5 or 10 ?? degress lower than at the top ( hmmm - unless the fan is not running - interesting ... )
I can't use a thermometer stuck into flowing water the top of the radiator cause then the water may boil at a little over 212? (with the cap off = no system pressure). I don't think that just "pressing" a meat thermometer against the fins of the radiator will give accuracy.

Also I don't know what the "too high" mark on the analog dash gauge is in degress - it's not marked in any numbers. So I don't know what temperture is by which, certainly, the radiator fan should have come on already.
Thanks

Its called the coolant temperature sensor/switch the computer uses its input signal for other purposes-such as fuel delivery, the engine temperature sensor at the radiator is the gauge sender and activates the cooling fan and gives the reading at the gauge