thermostat may be stuck open so engine doesn't get hot enough to blow warm air. Had the same problem on a Taurus once
the heat blows out the defrost when it should blow out floor vents only
you need a head casket
Likely, your blower (fan) is out.
Because the air selector died.
Fuel level, heat or air conditioning up, both high and low, high only, floor only. Center vents are for air conditioning output only, no heat. Heat is designed to blow out side and floor vents only. NOT center. Center is only for air conditioning or summer vents.
some thing is probley cloging the vents take it appart and ckeck.
Having the ceiling fan blow upwards will circulate the heat through the entire room.
So it has something to heat and blow back out, thus, heating your home. The stuff coming out of your vents has to come from somewhere..
somtimes a mouse moves into the blower motor and makes a nest ?
if it doesn't heat your heater core is most likely clogged and if it doesn't blow at all then the blower is messed up.
It sounds like your vacuum controls are stuck on the defroster I had that happen and I sprayed a lubricant into the vacuum lines and it cleared up
The most likely reason is your AC system needs recharged.