My heater is blowing cold air. All hoses are hot, thermostat is new, system flushed. I can’t find the blend door actuator. Is this the problem? How can I fix this?
That is definitely a possibility. Consequently it may also be a stuck blend door or damaged unit. There is also the possibility that a vacuum hose is loose or damaged. The blend door actuator should be located behind the center of the dash, on the left end of the HVAC housing. In the diagram the blend door is referred to as the temperature door. The actuator is referred to as a vacuum motor.
The heater unit houses the heater core, vent/defrost mode door, temperature blend mode door, and the fresh/recirculated air mode door. Coolant flows continually through the heater core. In conclusion the amount of heat is controlled by blending air across the heater core with fresh/recirculated air being vented to selected outlets.