...And then the needle dropped to zero...

[PanzerSD]

I get up for work this morning, hop in the car, fire it up and glance over my gauges and see that everything is on order, I drive to work (about 7 minutes)
Pull into my parking spot and just as soon as I put it in park, I saw the temp needle jump a little and fall to it's minimum energized position.

I say minimum energized position, because as the ignition is switched on the gauge comes up to that starting point (or when temp is much below 40*) If just won't rise to indicate the rise in tempurature. Is this likely to be a gauge fault, or a sensor fault? Is the sensor that is in my M617 the same that would be on my M117?