another temp gauge/fuel gauge/voltage regulator thread

I've an update which is a bit concerning:

I did take out my Valiant for a drive to see how the temp gauge acts with a warmed up engine. The first interesting thing is the needle went straight to hot but went a bit back and stayed on the left line in the "hot" section after 10-15 minutes. After 20min, when I put the gear shift (column shift) into R, the temp gauge needle immediatly went down to halfway (or however you call this).

I decided to go home after that but the engine started to misfire and cut out 3 times, of course exactely then when I went downhill. This for sure is a sign of overheating but it had never done this before when the gauge didn't work.

Now the weirdest thing was when I was home I pulled the sensor connector but the temp gauge still moved...? How even is that possible? Might there be a grounding problem?

I haven't tested the sensor yet because the engine/water was hot, obviously.