Car heater problems.?

Posted: 15 Nov 2013 05:07 AM PST

I turn the key on turn the heater on but nothing comes out, I switch it back and forth from vents to floor and defrost and back again and It hear it switching the modes, I turn it from cold to hot and I hear the motor switching the temperatures but when I turn it on 1,2, 3, 4 nothing comes out. Why could be the cause?