If your blend door or doors are broken sometimes you will only get cold air coming thru the vents or maybe just hot air with no air conditioning. A blend door is short for Blend Air Door. There are other names such as temperature door, etc.. The blend door, blends or mixes the hot air with the cold air. There usually is an actuator motor that opens and closes the blend door a little at a time to adjust how much hot air and cold air to mix for the temperature setting you have chosen.

A common design flaw in these systems is the end point detection for door movement.  The catch is that over time the plastic doors cannot withstand the over-stress of the calibration routine and will break. When this happens, all control over heat and AC is lost.

7/4/2017 06:35:56 am

I read your article a second time so I could take in all the information. I agree with many of your views. I enjoyed this.

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