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Odd auto climate control behavior

Old 12-07-18, 08:19 AM
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Former5SFE
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Default Odd auto climate control behavior

I usually leave my 2015 in AUTO at the desired temperature (usually 72). I've noticed the windows can fog up doing this. I used to own a 2014 Cadillac ATS with auto climate, and it would automatically switch to windshield defog + lower level here and there, and the windows would never fog up. I don't know if maybe the car had a sensor to detect humidity or something. I've also noticed my girlfriend's 2015 Santa Fe with climate control will periodically switch to defog at times in the winter and not even let you switch back until it's done doing it's thing. Do our cars ever do this, or do you have to manually hit the defog button? I noticed during the fall that the car would automatically default to the A/C being on at all times when in auto, even if outside temps were in the 30's and 40's. I know the A/C will dehumidify as a natural function of the system, so I thought that was the reason why it would default to being on (ATS never did this however. You would only see the A/C light if it automatically switched to defog). The odd thing I noticed this morning when it was in the low 30's, the A/C was not automatically on. Halfway through my drive the windows started fogging up. I tried resetting it by hitting the OFF button, then hitting AUTO, but the A/C did not default to on. I can manually hit the A/C button, but this just seems like odd behavior to me. Is there something wrong with my system?
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Old 12-07-18, 09:37 AM
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arentz07
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Originally Posted by Former5SFE View Post
I usually leave my 2015 in AUTO at the desired temperature (usually 72). I've noticed the windows can fog up doing this. I used to own a 2014 Cadillac ATS with auto climate, and it would automatically switch to windshield defog + lower level here and there, and the windows would never fog up. I don't know if maybe the car had a sensor to detect humidity or something. I've also noticed my girlfriend's 2015 Santa Fe with climate control will periodically switch to defog at times in the winter and not even let you switch back until it's done doing it's thing. Do our cars ever do this, or do you have to manually hit the defog button? I noticed during the fall that the car would automatically default to the A/C being on at all times when in auto, even if outside temps were in the 30's and 40's. I know the A/C will dehumidify as a natural function of the system, so I thought that was the reason why it would default to being on (ATS never did this however. You would only see the A/C light if it automatically switched to defog). The odd thing I noticed this morning when it was in the low 30's, the A/C was not automatically on. Halfway through my drive the windows started fogging up. I tried resetting it by hitting the OFF button, then hitting AUTO, but the A/C did not default to on. I can manually hit the A/C button, but this just seems like odd behavior to me. Is there something wrong with my system?
I have had this happen on rare occasion. Usually it stays defogged, but once in a while, particularly if I've been driving for a while, it will get fogged up and require me to manually activate the defogger. Like I said it only happens once in a while. On my commute I just leave it in Auto.
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Old 12-07-18, 09:59 AM
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JDR76
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It's been awhile since I've owned my IS, but I would have this happen on occasion as well. I'd leave it in AUTO all of the time except when I needed to manually put it into the defogging mode.

My GS has a physical humidity sensor mounted on the windshield and can automatically switch to defogging, while still in AUTO. I don't recall the IS having that sensor.
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