THERMOSTAT, HEATER CORE, COOLANT LEVEL & BLOWER MOTOR ARE ALL GOOD. WHAT ELSE COULD BE WRONG & HOW DO I FIX IT?
I HAVE NO HEAT. on 2004 Ford Explorer Sport Trac
Most Ford explores have a vacuum operated valve in the heater line to the heater. It is located on the passenger side towered the back of the engine in one of the heater lines. You should be able to move valve with your hand. Once engine is up to temperature, feel both sides of heater hose before and after valve. it should be hot on both sides if water is flowing. If not move valve and see if it gets hot on both sides. If that it is the problem, just prop valve open until you can replace it.
I would also check your blend door , fords are known for broken heater boxes