john omer

hi can anyone tell me please why when i put the heater on it dont come on but if i leave it on after a while it comes on it blows out heat out. if you turn it off and put it back on its no problem it comes on no matter how mant times you turn it off and on. but when the car is cold it dont come on. when you turn it on you can hear noises its making but it dont come on. thanks