Actually i once came across this problem. It happens after 2 months of buying brand new city. Servant left radiator cap open. I went far away. Went to hill station even, then back and started spinning a harsh driving where i found loss of power and change in noise of engine. Mean after about 2 hrs of real hard driving with AC on, at last that red light of over heating came on. I decided to go home and then check the problem. Before reaching home, it started blinking. Well went home safe n everything remained safe. Nothing unusual happened after that.
Purpose: Pani sar se nahi guzarta. 1st it turns on the light aur jab pani sar se guzarne lage, it starts blinking