heater blows cold air when turned on on 1996 Ford Explorer

heat was fine turned car off for a minute started it up no
heat. blows cold air. can here it change from vent to defrost to floor but no heat.

Asked by for the 1996 Ford Explorer
There is a motor in the dash that controls the blend of hot and cold air. The temperature blend door actuator could be failing, causing the door to stick on "cold".