My heater stop working

Hi,

I don't believe this vehicle has a heater core temperature sensor. I have a feeling you are looking for what is called the blend air door (aka temperature blend door actuator). That is what controls the air temperature entering the vehicle.

The actuator is under the dash on the passenger side. See pic 1 below.

Here is a link that shows in general how one is replaced:

https://www.2carpros.com/articles/replace-blend-door-motor

Here are the directions specific to your vehicle for replacement. The remaining pics correlate with the directions.

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2005 Mercury Truck Mariner 4WD V6-3.0L VIN 1
Temperature Blend Door Actuator
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Procedures Temperature Blend Door Actuator
TEMPERATURE BLEND DOOR ACTUATOR
TEMPERATURE BLEND DOOR ACTUATOR

pic 2

Removal and Installation
1. Lower the glove compartment door.
2. Turn the temperature selector to the full cold position.

pic 3

3. Release the locking tab and remove the temperature blend door actuator from the blend door shaft.
4. Remove the instrument panel center finish panel.
5. Remove the temperature blend door actuator.
6. To install, reverse the removal procedure.

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If you have no heat, first make sure the engine coolant is full. Also, pay attention to the engine temperature. It needs to warm up to operating temp for the heater to work properly.
Here is a link that goes over the most common causes of no heat:

https://www.2carpros.com/articles/car-heater-not-working

I hope this helps. Let me know what you find or if you have other questions.

Take care and God Bless,

Joe