I have a 2005 Mountaineer with no heat. What could it be other than a thermostat on 2005 Mercury Mountaineer

fans work, coolant is where it should be. Where else can I check, before taking it to a shop?

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No heat inside , but is engine warming up properly? Temp guage acting normal? Hoses under hood HOT like they should be? If so , problem may be blend door actuator (controls airflow through heater core/evaporator).Manual or automatic climate controls?