On "b", there should be NO resistance to ground...that is a thermistor with a return circuit, so it does not use a casing ground on the sensor.. I am assuming you are ohming across the sensor with it unplugged.
If you have a casing ground on the sensor, the sensor is bad ...if NO , then I can give you the Temp/Ohms chart for sensor calobration verification...

Another tip I will give you is many guys bridge the pigtail sensor right where I had you jumper test it with a two wire cord that they bring back into the cabin with a toggle switch...that gives the operator a manual over-ride for additional air-flow from the low fan any time one deems it needed..[ like towing or extreme traffic conditions, etc]..this over-ride does nor affect the a/c low fan circuit, but gives you that added air control manually..something to consider.

One of the most common mis-diagnosed complaints I see with engine overheat when car is at idle or in traffic w/ac on is the low fan does not come ON simply b/c the refrig is low...but it is border-line low, meaning you have a/c cooling , but b/c you do not have quite enough to trigger the low fan when the car is not moving, the coolant temp rises by passive heat load exchange from the a/c condenser to the RADIATOR ...so guys see an over- heat condition and start all kinds of thermostat and radiator changes ,water pumps, etc,...when the proper diagnosis is the refrig level is slightly low, causing no low fan b/c of cut-in spec of sensor...simple as that..no airflow over condenser/radiator when it is needed the most...even some Techs miss that one.............

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A Dalton