But if you called it coolant temp sensor, one might be confused it with something PTC when they whip out their multimeter to test it<pet peeve>
Which is precisely why it's a daft name to use to describe the coolant temp sensor. All temp sensors are either NTC or PTC. (Resistance decreases or increases as temp rises).
Difficult to test it properly without a list of what resistances correspond to what temperatures - whichever way they go... OTOH, if you're just doing a quick'n'dirty test, it's more important that the change is smooth, without any sudden changes or leaps to open-circuit or dead short - again, whichever way...But if you called it coolant temp sensor, one might be confused it with something PTC when they whip out their multimeter to test it
Depends which kind you have. The earlier c900s and maybe all c900s in some markets had the "Aut. Heated Seats" with the thermostatic switch in the cushion as you describe. When the seat-foam gets old, these button-shaped switches poke me uncomfortably. Later c900s (In USA) and 9000s had heated seats (at least the driver's seat) with what some call a "rheostat". This was not a rheostat. It was really a thermostat in a three-position-plus-off switch that read temperature from a thermistor in the seat cushion and compared it to a set point (setting 0, 1, 2, or 3 on the switch). I just retrofitted one to my driver's seat after soldering the broken element back together in 8 places. Bless the good man who invented heat-shrink tubing! My bµm is toasty.I don't believe they are. Just a simple thermostatic switch. No thermistor there.