I have an extra instrument cluster, so I swapped that whole left side unit and the problem went immediately away. The other one would give the correct temperature most of the time, but still when it jumps up your mind has to start to wonder if this is a true overheat. Mine was not an electrical connection on back, as I had scotch-brited all pins and had it in and out a good 10 times for speedo cable, odo. repair, lights, etc...
JL