AC Issues in Humid Environment

[Steven Gallier]

I have a 2007 Expedition with AC issues in humid environments only. I live in west Texas and the AC works just fine. But every time we travel to a humid environment like Louisiana it starts blowing warm to hot. Once we head back west the further we get passed Dallas the better it starts working again. I've taken to a Ford mechanic and they can't seem to find the issue mainly because I can't recreate the problem in this dry environment. Any help would be greatly appreciated.

 

[outdare]

My guess is the evaporator is full of dust. So when in humid area's it is just packed and no air goes across it.

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[Yupster Dog]

Or the vent recycle door stuck on vent.

 

[vincentrose]

In humid environment the A/C creates more water, and the evaporator is freezing and blocking or severely reducing the airflow through it, you also may notice the air coming out of the vents is not as powerful when it freezes. you can test this theory if you ever go back to Louisana, when the airflow out of the vents becomes less and less, turn off the A/C but leave the blower on. This will allow the ice on the evaporator to melt, you may notice the air coming out still cold, because the ice is still there, when the ice has melted the air will start to get warmer and you can turn the A/C back on. If is happens the culprit is most likely the evaporator temperature sensor. The climate computer is suppose to monitor this sensor and cut off the A/C compressor when the temperature at the evaporator the drops to near freezing (like 34 degrees) and turn the compressor back on at around 37 or 38 degrees. If the sensor is bad the compressor will just run all the time which causes the evaporator will freeze up in humid conditions.