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Discussion Starter #1
Wondering if anyone else with climate control has this issue or even noticed it. My wife keeps the climate control set to auto and has it at 70. I noticed yesterday while in the Jeep with her that the drivers side window was fogging up and the windshield so she pressed the front windshield defroster button. When she did this for some reason the max ac button lit up as well like it was changing from heat to ac. Again later I was driving this time the windows started to fig up again so I hit the defrost button and yet again the max ac button lights up as well. Seems odd to me that the ac should come on when you push front defroster button. Wondering if anyone else has noticed this when switching from auto to front defrost?
 

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This is normal. Most new cars do this. Running the AC dries the air. The AC will condense the moisture out of the air. Since it is moisture that is condensing on the window, if the AC condenses rhe moisture first there will be less water in the air to condense on the window. I was taught when I was young to turn the AC when you need defrost, this car just does it for you. (It still routes the air over the heater core so the air will still be warm)
 

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Discussion Starter #3
This is normal. Most new cars do this. Running the AC dries the air. The AC will condense the moisture out of the air. Since it is moisture that is condensing on the window, if the AC condenses rhe moisture first there will be less water in the air to condense on the window. I was taught when I was young to turn the AC when you need defrost, this car just does it for you. (It still routes the air over the heater core so the air will still be warm)
So basically its still blowing 70 air while using the AC as a dehumidifier to take the moisture out of the air inside the car and stop the windows from fogging?
 

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This is normal. Most new cars do this. Running the AC dries the air. The AC will condense the moisture out of the air. Since it is moisture that is condensing on the window, if the AC condenses rhe moisture first there will be less water in the air to condense on the window. I was taught when I was young to turn the AC when you need defrost, this car just does it for you. (It still routes the air over the heater core so the air will still be warm)
So basically its still blowing 70 air while using the AC as a dehumidifier to take the moisture out of the air inside the car and stop the windows from fogging?
Yep. Well sorta anyway. If you have the car set to 70 the system isn't blowing 70 degree air. It's blowing whatever temp air it thinks it needs to get the cabin to 70 degrees. If it's warmer than 70 in the car it will be blowing colder air, if it's colder than 70 it will be blowing hotter than 70 degree air. The bigger the difference of actual temp and set temp, the bigger change in air temp blowing out of the vents.
 

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Chris got this one already, but just to reiterate, it is 100% normal and I wouldn't expect any other type of behavior from a car these days. As far back as I can remember, the AC always turns on with the defrost. Most people associate "AC" with strictly cold air, but its function is true to its name, and all it does is condition the air. Yes, 99% of the time its because we're using it to make the air colder, but in a vehicle its also necessary for the defrost to work properly.
 
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