Fiesta IV 1.3i endura cooling sensor

Hi everyone. I own a Fiesta IV (1.3i 44kw 1999 year). I noticed a malfunction of the cooling circuit: the thermometer  indicates an average low temperature of the liquid, but when I'm in traffic lined up the needle more than half of the sector, but it never reaches the red sector. By contrast, however, in this last situation I realize that the fan will run late because the actual temperature of the liquid is high because I feel the hum of boiling and cooling sleeves are hard to elevated pressure. At this point, I deduced that the temperature sensor informs the ECU which provides for activating the electric fan relay and the thermometer. The problem is that I could not locate it on the engine. I could not say if what I gather is responsive to the reality and where the sensor is positioned and, in the model in question, what color is it? Thank you