any advice on slow fan speed (heater)

What is your question?

when running idle it seems to be building heat but there is little to no fan/blower speed to heat/defrost the cabin,when traveling it seems to pick up and blow a little harder but not much.also it doesnt seem to change speed regardless of the fan speed setting i put it on (solid fan,auto or the lower setting.any help or advice will be greatly appreciated.thank you..