cooling fan not working. on 2001 BMW 325Ci

what i need to do to check the fan function.

Asked by for the 2001 BMW 325Ci
There is a 4 pin plug on the passengers side of the fan. Power and earth and 2 small wires with modulate the fan speed.
I am not aware of anyway to check it beside via BMW tester machine.
When the A/C is switched on fan speed one should be engaged within few seconds. Fan speed two should only come on when car is getting too hot