Thank you, aefron88.
My ordered switch came today, and I installed it. Before I installed it, I extracted the coolant through top radiator with the pipe reach its bottom. Only about 200 cc came out, so when I removed old switch, almost no coolant came out from there. After I installed the new one, I poured back the extracted coolant through top of radiator.
I'll test runs to see if fan runs when engine/coolant is hot enough ( I believe at least 75 C), and also if overheat happens due to air in the system and requires bleeding.