Griff in Fairbanks wrote:
On the case of engine temperature, the sensor has a wax/plastic plug that melts and solidifies over a range of temperatures, increasing or decreasing resistance in the circuit. Over time (decades), the plug loses its ability to respond to temperature changes.
Okay, 'my' take-away from this? (and thanks for that tid-bit of information, Griff!! Something REALLY nice to know when troubleshooting sensor-dependent circuits!) If you don't know how old a sensor is and if/when it was last replaced, it 'might' be a good idea to replace it anyway.
