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Discussion Starter · #1 ·
Has anyone figured out how to stop the HVAC system from using the defrost vents to precondition a hot car when using the app (Onstar)? It's not every time, but it happens often enough to be annoying. I first turned off the auto defog to see if this might help. It was hard to tell if it improved or changed.

I also noticed this happens a lot more often if I'm using a sunshade. But I don't really want to stop using it since the car will get a lot hotter.

The few times I've used the keyfob instead of the app I've never seen this happen. Any help out there? The car doesn't cool down very much when all the cool air is blowing onto a hot windshield.

Keith
 

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I think this topic came up before, probably with the Gen 1.

Have you tried setting your HVAC system by manually selecting the dash vents before turning off the car? I think the car is supposed to follow your settings during remote start.
 

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I frequently use the precondition cycle to run the AC in summer when my 2017 Volt has been sitting in my hot garage or baking in the sun. The only issue I have with the climate control selecting the defrost vents is that I get condensation on the outside of the windshield when the humidity level is high and the windshield cools enough to condense the moisture on the outside of the glass. One or two passes of the wiper blades will clear the condensation. When parked outside, I have never had a problem with the Volt not cooling down sufficiently as long as I let it run for at least 8 minutes of the full 10 minute precondition cycle. I do use a sunshade when parked outside. My windows are not tinted other than the factory tint. Inside my garage [Updated] I have timed this now, 4 minutes of AC running will cool down the Volt's interior when set to Auto, Max AC, 70F, recirculate Off. The AC compressor and fan initially ran at a high speed for about 3 minutes, then throttled down to a medium speed. This test was run earlier this evening when my garage was a very warm 94.5 F, this was down from measured daytime high temperature inside the garage of 99 F. Even though my Volt was slow cooking inside my garage all day while it was plugged in I did not notice the Volt turn on the fan or AC compressor to cool the battery during the day. The mass of the battery, ~ 450 lbs as I recall, takes a long time to reach the set temperature point that will cause the Volt to start the battery cooling cycle. It does happen but not as often as I would have expected, usually happens when I am charging at home and the garage temperature is above 90 F. I did not remember to check the engine coolant temperature when I was still inside my garage but about a half mile from home the coolant temperature display read 100 F. I realize that the engine coolant and the battery coolant are on different cooling loops, I was only trying to determine the temperature of the Volt's systems prior to running the preconditioning cycle. Perhaps the battery coolant temperature was significantly lower than 100 F prior to the preconditioning, the Volt does not provide this information via the normal Driver Information Display.
 

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I think this topic came up before, probably with the Gen 1.

Have you tried setting your HVAC system by manually selecting the dash vents before turning off the car? I think the car is supposed to follow your settings during remote start.
I am the one who brought this topic up before. This happens frequently on MY2012. If I use the fob, the AC blows from the vents, if I use OnStar, a good 85% of the time it comes out of the defrost. It does not matter how I manually set the controls, the system over rides it, and the moment I hit the power button the air changes to the vents.
 

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I am the one who brought this topic up before. This happens frequently on MY2012. If I use the fob, the AC blows from the vents, if I use OnStar, a good 85% of the time it comes out of the defrost. It does not matter how I manually set the controls, the system over rides it, and the moment I hit the power button the air changes to the vents.
I tested it this week, I get the same results with my '13

A touch annoying as my sunshade slightly blocks the vents. Much like the OP though, I'm not going to stop using the sunshade.
 

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Strangeness at work here I think. I don't precondition too often, but when I have, and open the door to get into my '13 its always blowing out of the dash vents as normal. Usually it's allowed to run a few minutes so maybe it's starting at the defrost vents, but it's definitely blowing through the dash as I always check how cool it's blowing from the outer drivers side vent before getting into the car. I never use the onstar app but instead the fob, but perhaps this afternoon I may give the app a try and see if the result is different.
 

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Strangeness at work here I think. I don't precondition too often, but when I have, and open the door to get into my '13 its always blowing out of the dash vents as normal. Usually it's allowed to run a few minutes so maybe it's starting at the defrost vents, but it's definitely blowing through the dash as I always check how cool it's blowing from the outer drivers side vent before getting into the car. I never use the onstar app but instead the fob, but perhaps this afternoon I may give the app a try and see if the result is different.
I can do 2 full cycles, getting in the car at the last of the 2nd cycle and it is still blowing out of the defrost. I don’t have this issue at all when I use the fob. My solution was to park my car closer to my desk so I can use the fob in the summer.


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Discussion Starter · #8 ·
I set the HVAC direction control to the dash at lunch today, and I'll try it for a few days and see what happens.

Based on the experiences above, I'm not terribly optimistic.

Keith
 

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I just stepped out to grab lunch. My Volt was parked inside my garage. Climate control settings were Auto, Max, 70F, Cabin Air Recirculate set to Off. I used the MyChevrolet App (the latest version of the Mychevrolet App allows you to use Touch ID instead of entering a PIN to start the Preconditioning.) As previously noted, the Volt AC started and ran using only the Defrost vents blowing cold air at the windshield and the side vent window area (the two little vents located above the dash vents.) On the way home I used the key fob to remote start the Volt and this time the dashboard vents were blowing cold air. One possible explanation, since the Volt designers could not know whether the Preconditioning would be run in summer or winter, maybe they did not have the ability to tie the HVAC setting to the outside temperature, they opted for using the defrost vents for preconditioning so that this would defrost the windshield in winter.
 

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I set the HVAC direction control to the dash at lunch today, and I'll try it for a few days and see what happens.

Based on the experiences above, I'm not terribly optimistic.

Keith
Tried this too, no luck for me. I finally gave up.


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This A.M. I started my Volt, set Temperature to Low, turned off the following HVAC controls: Max, Auto, HVAC On/Off all set to off. Turned off the Volt. Ran the Preconditioning cycle via the MyChevrolet App. Cold air started blowing at high speed from the dash vents. It appears that you can control how the MyChevrolet Preconditioning cycle behaves based on the temperature setting.

[Update #1] Tried the above settings except temperature was set to 65F. Preconditioning via MyChevrolet used the Defrost vents.

[Update #2] Tried Preconditioning with temperature set to 61F and 62F, cold air started blowing from the Dash Vents.

[Update #3] Tried Preconditioning with temperature set to 63F, cold air started blowing from the Defrost Vents.

In summary, if you want to be sure that the Dash Vents and not the Defrost Vents are used during warm weather preconditioning of the Volt via the MyChevrolet App you must set the climate control temperature to 62F or colder.

If you use the key fob to remote start the Volt the HVAC will use whatever setting you had when you last turned off the vehicle.
 

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Discussion Starter · #12 ·
I set the HVAC direction control to the dash at lunch today, and I'll try it for a few days and see what happens.

Based on the experiences above, I'm not terribly optimistic.

Keith
I had a couple good days where the A/C was blowing correctly, but yesterday it was coming out of the defrost vents. So, as expected, setting the flow manually didn't fix the problem.

Perhaps during the next round of hot days I'll try setting the temperature control lower as suggested above.

Keith
 

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Sadly, even if setting the temp to its lowest possible setting causes the vents to blow correctly, is still not a good solution for me. I use the Auto feature so I don’t have to fuss with the controls.


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Discussion Starter · #14 ·
Perhaps during the next round of hot days I'll try setting the temperature control lower as suggested above.
This failed too. I set the temp control to Low and mode to Max during a recent round of hot weather, and on the very first day came out to air blowing (at a relatively low speed to boot) from the defrost vents. I didn't even have the sun shade up.

Oh well.

Keith
 

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Hmmm.... I'm not entirely sure where I'm going with this thought, but I do know that when air temperature drops, the relative humidity goes up without actually changing the amount of water in a volume of air, until it eventually condenses and rains. The only mention so far is in post 1, which was a "couldn't tell if it made any difference". Maybe there IS a switchpoint that's based on humidity more or less alone that says "it's humid enough in here we're going to need some precautionary window clearing".
 

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Hmmm.... I'm not entirely sure where I'm going with this thought, but I do know that when air temperature drops, the relative humidity goes up without actually changing the amount of water in a volume of air, until it eventually condenses and rains. The only mention so far is in post 1, which was a "couldn't tell if it made any difference". Maybe there IS a switchpoint that's based on humidity more or less alone that says "it's humid enough in here we're going to need some precautionary window clearing".
There might be something to what you stated, if you have Auto Defogger set to Yes then the Volt may choose to use the windshield defroster vents during preconditioning regardless if the AC Temperature is set to Low (or less than 63 F). My experience is that when the Defroster Vents are blowing cold air moisture will condense on the outside of the cooled windshield and require use of the wipers to clear the windshield fogging on the outside of the windshield near the defroster vent area.
 

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There might be something to what you stated, if you have Auto Defogger set to Yes then the Volt may choose to use the windshield defroster vents during preconditioning regardless if the AC Temperature is set to Low (or less than 63 F). My experience is that when the Defroster Vents are blowing cold air moisture will condense on the outside of the cooled windshield and require use of the wipers to clear the windshield fogging on the outside of the windshield near the defroster vent area.
Unfortunately I can rule out the auto defrost option. Toggling the setting has made no difference in my testing.


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