An example non-transitory machine-readable storage medium includes instructions to determine whether a cooling fan is controlled by pulse wave modulation (PWM) or is voltage-controlled. When executed, the instructions cause a processor of a computing device to transmit first and second PWM test signals at different PWM duties to a fan connector connected to the cooling fan, receive a first and second fan speed signals in response, and determine, when the first fan speed signal is not equal to the second fan speed signal, that the cooling fan is a PWM-controlled fan. The instructions further cause the processor to transmit first and second voltage test signals at different voltages to the fan connector, receive a third fan and fourth speed signal in response, and determine, when the third fan speed signal is not equal to the fourth fan speed signal, that the cooling fan is a voltage-controlled fan.