Junk equiss gauges?

i chased an over heating problem for some time years ago.210 plus idling in heat..not real hot but concerning.Tried a new equus temp gauge (the second new one) just to be sure and there was no change.
Bought a new rad and still ran "a little hot at 200 plus.Then i purchased a new Stewart Warner Temp gauge and the Dart never went over 190 from that point on. Lesson learned!
i have had failures with bottom line auto meter tachs as well.