1996 Honda Accord EX heater

My heater has stopped working. You can feel heat from the motor coming through the vents and you can switch it to cold and feel cold air coming through the vents also. It doesn't matter if you have the dial turned to low or high you still feel the same amount of air coming through the vents. When you turn the dial to turn the air on you can hear something in the dash of the car and it sounds like the heat wanting to come on, but then it doesn't come on. It was only coming on once in a while then it stopped all together. I replace the thermostat and the heat worked for about two days then it quit.