Please read this carefully before posting comments or answers. This is NOT an overheating issue. It is just about cooling system behavior under specific conditions.
My car cooling system has two fans which operate in two different modes. The first mode is low speed operation which means the fans run with 6V power at half speed. In this mode, they turn on when the engine temperature reaches 95-96 degrees and turn off when it reaches 92-93. The second mode is high speed operation which involves the fans to run with 12V power at full speed. In this mode, they turn on when the engine temperature reaches 105 degrees and turn off when it reaches 101-102. When A/C is off, high speed mode is never activated because in low speed mode, fans have enough power to keep the engine cool.
Today, I was driving up an uphill highway for 20 minutes (in 4th gear) and the outside temperature was about 39 degrees Celsius (102 degrees Fahrenheit). I noticed the temp gauge reached about 96 °C (when low speed mode turns on). I continued driving uphill and the temp showed 97 and even 98 °C. It didn't go higher and stayed there (between 97-98) and started to go lower (between 93-94) when the slope of the road decreased a little bit.
Why couldn't the fans bring the temperature back to 93 °C when I was climbing the steep road? Is it normal that cooling fans operate but they only manage to keep a steady engine temperature in a steep road? In most cases when low speed fans kick in, they lower engine temp but today this didn't happen. Why?