Engine coolant temperature sensor issues

Today I attempted to test my ECT sensor. The procedure went like this:

  1. Boil some water
  2. Connect my multimeter up to the sensor
  3. Dip the sensor into the water and take occasional temperature readings. Compare the resistance readings to the temperature to see if they should be where they are expected

I did all this and got wildly unexpected results. Way higher resistance than I expected. For reference, here is the chart showing what I should have seen.

Part # 1346030

Looking at the sensor I noticed that it actually wasn’t Bosch branded. It was made by Spanish manufacturer Francisco Albero S.A.U (aka FAE). I’m not sure that company was ever an OEM supplier to Volvo, so I’m sort of suspecting that this sensor had been replaced at some point and that the not so good FAE replacement has since failed. Regardless, I have a Bosch replacement on the way. Since this thing is such a pain to access I want a good part going in before I reattach the intake manifold.