it should be close to the fan in the front of the evap case. passanger side firewall engine compartment
check the heater control valve. these things tend to stick either open or closed. it may also be your blend door. check the heater control valve first, for you dont have to take the dash off.
If by quit working you mean quit blowing, the things to troubleshoot are the blower motor, the blower motor resistor switch, or the blower motor speed selector switch. If by quit working you mean it only blows cold or warm air, the thermostat is probably stuck in the open position.
The diverter, or blend, door, is not working properly, The door is either feeding the heat through the defroster, or closing the heat completely off.
Check your fuse
because it broke.
When you have the heater on, does it just blow any air at all? or no air?
Flush your radiator coolant and replace thermostat
That or the thermostat.
You have a bad blower resister..............
Quit Trying to Steal Trucks!!!! Ford Tech's don't even Have this Info.
Check fuse if the blower is not working. If it is then replace your heater core. if its not then replace your fan switch.
loss of power after,or with black smoke , indicates the turbo has quit.