[quote pid=1199 author=dannyb.G40 date=1209937471]With regards to testing:
Does the engine need to be running?
How do you know how hot the coolant is?
Does the sensor have to be removed to get to the poles?
(I study an electronics module at uni and still dont understand how it works). Any help much appreciated as usual![/quote]
To get the figures I quoted above I removed the sensors from the car, plugged in some flying leads to them, and stuck them in to a bag with a type K thermocouple.
I measured the resistance first at room temp (20°C), then stuck them in the freezer for a few hours to give them time to soak (-7°C). After that I stuck them in a collander above some boiling water (95°C). I nicked Yoof's multimeter with a type K thermocouple input so I could measure the temperature as well as the resistance.
The above method's not hugely accurate - but the sensors vary hugely and the tolerances on the input are so large that it doesn't matter. It's more than sufficient to see if you sensors are working or not.