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Why would my temp reading stay below normal operating range?
2005 Ford Explorer

Why would my temp reading stay below normal operating range?

(2005 Ford Explorer)
My 05 4.0 explorer seems to always run cold,,, not hot but cold.. temp shows below normal range regardless of outside temp, driving distance and or while towing. I do have heat, however the air only comes out of the defrost vents no matter where the selector knob is placed.
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Popular Answer
Hello Mr. Mahaffey,

Thank you for reaching out to us. It sounds like you may have a thermostat that is stuck. The thermostat will open and close based on the temperature of the vehicle via a mechanical heatspring. Over time, this spring wears out or becomes fouled with debris in the cooling system and ceases to close or open. When stuck open, a lot of times it will prevent the vehicle from reaching operating temperature which can be almost as detrimental to the life of your engine as an overheat condition. The thermostat can also without warning unstick itself, and stick in the other direction, i.e. from fully open to fully closed, which would then overheat the engine very rapidly. This is a serious driveability concern and should be fixed as soon as possible.

The air blowing from only the defrost vents is most likely an issue related to what is called a blend door assembly. This assembly will proportion the air correctly to provide the desired temperature as well as direct the airflow to the selected channels. Hope this helps!
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General Diagnosis
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Hello Mr. Mahaffey,

Thank you for reaching out to us. It sounds like you may have a thermostat that is stuck. The thermostat will open and close based on the temperature of the vehicle via a mechanical heatspring. Over time, this spring wears out or becomes fouled with debris in the cooling system and ceases to close or open. When stuck open, a lot of times it will prevent the vehicle from reaching operating temperature which can be almost as detrimental to the life of your engine as an overheat condition. The thermostat can also without warning unstick itself, and stick in the other direction, i.e. from fully open to fully closed, which would then overheat the engine very rapidly. This is a serious driveability concern and should be fixed as soon as possible.

The air blowing from only the defrost vents is most likely an issue related to what is called a blend door assembly. This assembly will proportion the air correctly to provide the desired temperature as well as direct the airflow to the selected channels. Hope this helps!
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