420sel heat thru the vents

i cannot seem to get warm air to flow thru the vents in the dash, only the floor and under the front seats. what is the ideal way to set the air flow slides to get warm air throughout the car. in addition, i only get cold air out of the defrost when the climate control is set on the economy setting. am i just stuck with this or does something need to be replaced. any thoughts are much appreciated. thanks