Question

how does the engines get cooled when the vehicle moves in a hill ramp.?i ask this question because its said that cooling fans are drived by the rotation of the engines sothat the cooling fans are mounted in the engine casing.If that's is the case then at ramps engine run slowly due to that rotation of cooling fans will be low and heat radiator will increase if im wrong please tell me that wherean cooling fan gets power and how it works in ramp?