E39 temp gauge

[dodoluvs38aces]

E39 temp gauge
Hi guys. I've got a '99 E39 540i 6-speed. I absolutely love this car. My problem just started yesterday. My temperature gauge will shoot all the way to the red, not gradually. At the same time my speedo & tach will die; and the AC will no longer blow cold and if cruise control will disappear. I've already established my cooling system is fine but its very unnerving for the temp gauge to shoot all way to the red in a moments time. Its very erratic happens intermittently. It will go back to normal later on its own.
Does anyone know what this electrical gremlin is, why its happening, & any workarounds or solution(s).
All input is welcome and appreciated. Thanks

[hakentt]

check if you see any water or corrosion on DME/ECU plug pins