Radiator fan comes on after vent fan is turned on even on cold engine. It goes off and on from time to time an turning off completely after vent fan is turned off. Civic 2009

 

That is normal when you have the selector set to defrost. Regardless of the setting of the A/C button, the air conditioner comes on to dehumidify the air hitting the windshield and clear off fog faster. Whenever the air conditioner is on the radiator fans run to cool the condenser.

 

Thank for replay
Actually defrost is off and AC off (it was even in winter time)
I tried it not turning on engine(just turn ignition key to ON) and both fans(radiator and ac) still on