My ecu turns my fans on at 95C and off at 92C, but on the gauge reading this can be anywhere between the bottom edge of the "M" to mid way between the "N" and "O", even though it at the same temp each time in reality.
Even though the fan wiring etc looks right, it needs doing, the wiring is 20+ years old etc, just not worth the risk, was pretty crap to start with, and that was 20 years ago!!
tabetha