HVAC Blowing Defrost

MudPump · February 8, 2018

If you push this button on a 2014+ GM/Chev, does your truck keep blowing an annoying amount of air out the defrost vent? I had heard there were updates to the HVAC module, but don’t know if it changes the behaviour. If yours is newer and doesn’t blow out the defrost, lemme know so I can take it to the dealer. I had been dealing with it, but now tired of the extra noise, surprised it works this way. That button implies floor heat only, no?

BO TIE 1 · February 8, 2018

My 2018 blows floor only and so did the 2014 I traded in.

MudPump · February 8, 2018

I dont think its actually blowing, maybe just sounds like it is. Its the same sound when its on floor/defrost, but just no air coming out defrost? Just crappy that it has to be that loud. I end up turning it on floor and dash vents, and then just close the dash vents. Makes for a much quieter ride.

Logan Lanfear · February 8, 2018

You might be missing some piece of insulation that goes around the valve? If no air is coming out of the defrost then I would think its slightly normal?

Hoginedgewood · February 8, 2018

I’m thinking they have a small opening so a tiny bit of air always hits the windshield. I hear it from the dash when it’s on HI! But the lower the speed the less I hear it.

Mines a 17

could lay a piece of paper or a tissue to see if it is noise or air.

Stronger800 · February 10, 2020

Trying to bring this back up

Stronger800 · February 10, 2020

As my '18 just started doing this yesterday. I traded in a ford....because I got mad it it after having a blend door actuator replaced 3x under warranty. My gmc did Not use to have this wicked noise coming out of the defrost vents when " floor" or "floor/dash" was selected....but it does now. Extra noise drives me Crazy. 20k miles on it. I'm dreading calling the dealer. They won't have whatever it needs in stock, if, they even can determine that it has a need. They'll most likely tell me it's normal, or that "technician unable to verify concern".

Donstar · February 10, 2020

1 hour ago, Stronger800 said:

I'm dreading calling the dealer. They won't have whatever it needs in stock, if, they even can determine that it has a need. They'll most likely tell me it's normal, or that "technician unable to verify concern".

This sounds like how I feel when going to the doctor! I find the fan too loud when it is on its highest setting. I seldom use the highest setting but it will come on automatically when there is a significant gap between the requested and actual temperature. I simply turn it down and keep cool for awhile longer!

Stronger800 · February 10, 2020

5 hours ago, Donstar said:

This sounds like how I feel when going to the doctor! I find the fan too loud when it is on its highest setting. I seldom use the highest setting but it will come on automatically when there is a significant gap between the requested and actual temperature. I simply turn it down and keep cool for awhile longer!

Has anybody had this repaired? Was it the switch? Sensor? Blend door actuator?

JimCost2014 · February 10, 2020

32 minutes ago, Stronger800 said:

Has anybody had this repaired? Was it the switch? Sensor? Blend door actuator?

Question, are you sure the noise is coming from the vents?

Have you ever changed your cabin filter, if debris gets caught in the filter, or in the blower fan, it will make strange noises increasing with fan speed.

Stronger800 · February 10, 2020

1 hour ago, JimCost2014 said:

Question, are you sure the noise is coming from the vents?

Have you ever changed your cabin filter, if debris gets caught in the filter, or in the blower fan, it will make strange noises increasing with fan speed.

I have not. But it's not a something stuck in fan noise. It's defroster blowing Up when it shouldn't be noise. Sound goes away 100% when switched to "floor/dash". But it's still there when switched to "floor"

Rob Armstrong · February 11, 2020

I have a 2015 GMC 2500 lose settings every time I shut it off date/time /radio anybody had this issue could it be a weak batt it always starts ?

Stronger800 · February 11, 2020

I just tested it a bit to verify it is indeed blowing air up through the defroster when it is suppose to be just directing it to the floor. When I select "floor"....it will blow a sheet of paper right against the winshield. When I selct "floor/dash" it doesn't