The recent thread on cooling fan issues brought this to mind dash gauges are designed to tell lies. This is image from an MG-Rover factory workshop manual ---- the temperature needle has zero movement between 75c and 118c amd they wondered why they had so many engines wrecked by major overheats. A nother example is the oil pressure "gauge" on Jeeps that is driven by simple pressure switch.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)