I don't see anyone PUSHING you to buy a sensor. I only see people answering your question as to what the blue sensor is and does .
But you somenow know the sensors is OK .. Well , I guess you did an OHMS/TEMP comparison reading with your Ohm Meter and have verified the sensor to be in Spec.
You posted that you are not familiar with the Fan circuitry, but when people who are familiar and do come to answer your posting, you accuse them of pushing to sell you a part???

We are here to aid you in a diagnosis and are pushing nothing more than fellow good will and knowledge.