I agree R-R, we are looking at a symptom to find a cause.
The reality is though, that in the air those symptoms are all we have. If I had access to the 2 types in question right now I'd be taking a look to see what is different about the installations, sensing technique, and anything else I could find, that could explain the readings. As much for curiosity as anything else. Then I would apply that to the type I'm on now to predict how it would react in real life.
As a pilot, I have used temps and pressures often to make critical decisions about the real severity of a malfunction: is it a gauge, a sensor, or a component that is in trouble? Very little of my flying has been over what could be called non-hostile terrain, and I take very seriously the trust that the people in the back put in me to make the right decision.
As an engineer, I want to provide a safe aircraft, and to know the machine well enough that when a pilot asks my opinion on it, I am confident of my answer.
I took a look at my old 212 notes and trying to think back. The notes are more reliable :-) A temp bulb for the gauge and a temp switch in the cooler output line for the light. I guess I'll have to wait until I can put my hands on them to really answer the question.
Cheers guys.