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2018 Defroster Runs Constantly

nashman50

New member
6
0
1
Buick Ownership
2018 Regal Sportback Preferred I
Hi Everyone,

I am having trouble with my 2018 Sportback. Even with the heat set only on floor, the defroster runs constantly. If I turn off the floor setting, it only blows out of the defroster, but not the other way around. Is this a setting for the humidity sensor? I wouldn't think it would be that as it has been dry here lately.

Does anyone else have this issue?
 

Jmlo96

Active member
106
76
28
Pittsburgh
Buick Ownership
19 Regal TourX Essence
I think these cars always blow a small amount of air from the defroster vents (at least when set to floor mode.) My 2019 TourX has a similar behavior to what you are describing. I noticed it sounds like the defroster is on but it's blowing out the floor vents.
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nashman50

New member
6
0
1
Buick Ownership
2018 Regal Sportback Preferred I
It seems to blow the same amount of air from the defroster if the button is pushed or not. It is still within the warranty period so I scheduled an appointment to have it diagnosed.
 

Uniqez

Active member
483
229
43
Buick Ownership
2018 Opel Insignia Country Tourer with Buick steering wheel, HMI and floor mats
Hi Everyone,

I am having trouble with my 2018 Sportback. Even with the heat set only on floor, the defroster runs constantly. If I turn off the floor setting, it only blows out of the defroster, but not the other way around. Is this a setting for the humidity sensor? I wouldn't think it would be that as it has been dry here lately.

Does anyone else have this issue?
Exactly the same happening on my car. As it was explained to me - this is controlled by humidity sensor. Try to blow hot air through the defroster on the cold weather and you'll see that it will be completely closed. I went through two dealerships- they were saying that I had to replace the HVAC unit. But the dealer that I'm servicing car now at said this is common, since you have so many algorithms in the HVAC, that it does some things base upon the data received from sensors in the car. If it thinks that humid level is high it would blow some air on the windshield regardless, if you selected it or not. He said they were working on LaCrosse and ended up calling GM engineers, because they've seen exactly the same. GM engineer had mentioned humidity sensor.
Later on, I've purchased my diagnostic cable and was able to look how the gates are moving - haven't seen anything abnormal. When they are closed - it does show 0 degrees angle.
 

capitalpyro

Member
32
28
18
Buick Ownership
Tour X
It seems to blow the same amount of air from the defroster if the button is pushed or not. It is still within the warranty period so I scheduled an appointment to have it diagnosed.

so what did you find out?
The defroster on my car works poorly no matter which setting. When set to defrost with fan at any speed, more air comes out of the rear registers behind the console than anywhere. Im not sure if there is a separate damper for that or what. Does anyone know exactly how the dampers work on this particular vehicle?
 

Uniqez

Active member
483
229
43
Buick Ownership
2018 Opel Insignia Country Tourer with Buick steering wheel, HMI and floor mats
so what did you find out?
The defroster on my car works poorly no matter which setting. When set to defrost with fan at any speed, more air comes out of the rear registers behind the console than anywhere. Im not sure if there is a separate damper for that or what. Does anyone know exactly how the dampers work on this particular vehicle?
It is some strange ( GM ) algorithm that takes into consideration ambient temperature, humidity and set temperature of the HVAC to calculate what diffusers to use. All I know- it will never-ever will let you blow hot air to your cold windshield.
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