about proton persona

hi,i have encounter 1 proton persona that i could not solve probably,when i start the engine until it was hot , the radiator fan turn on but i"m waiting until 2~3 minutes the fan motor still spining, i thought it was thermostat jammed and i have replaced it but the problem was the same result...

Does anyone know what is the problem that cause the fan motor keep turning non-stop after the engine is hot?