i have some questions about the coolant temperature sensor on the m103 2.6 in 1993.

First, ive noticed on ******** that there are 3 different coolant temperature sensors?

This is for CIS/EZL signals ?:
http://www.***************/secure/PartImages/0085423217.jpg

aux fan signal ?:
http://www.***************/secure/PartImages/0085424517.jpg

instrument cluster signal ?:
http://www.***************/secure/PartImages/0055421017.jpg

is that what those 3 sensors are for?

next question: how do I know that i plugged the 4 prong connector from the wiring harness correctly into the sensor at the back of the engine? there is no indication on which way it connects, ive just been plugging it in based on the orientation i remember from unplugging it in the first place. not sure how to verify that is the correct way it goes.

next question: how does this 4 prong sensor work? it looks like one of the prongs is ground, the other gives off a resistance of ranging from ~2000 ohm when cold and ~300 when engine is hot. the resistance based signal seems to be connected to the EZL on pin 1 based on a continuity test.

the other two signals I am not sure about, but one of them is connected to pin 21 on the ECU wiring harness (i suppose this is for controlling a/f mixtures), but how is that signal being generated? It does not give off any resistance, nor could I measure a voltage when tested against ground. should all 3 prongs be giving off resistance values and the one I have is broken?

other question: how does the instrument cluster water temp sensor work? is it based off a voltage or a resistance? i could not measure a resistance when tested against ground.

sorry for so many questions!