HVAC system ALWAYS defaults to A/C when first turned on ...

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inane222

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Good afternoon,

Newb to the forum here, this is my first post outside of my intro. Picked up a 16' XL Denali in November with 36K, got 39K on it now. I've noticed a strange behavior in my HVAC and wanted to ask the good folks here about it.

When we're finished driving, we turn the HVAC off before shutting down. When we get back in the car, we see the following (climate control is still turned off):

1. Temp is still set where it was at shutdown.
2. Sync light is illuminated on the passenger side knob (I keep this active to keep the temps the same)
3. Light is illuminated on the last airflow position button (usually on the bi-level position)
4. Power button indicator is not illuminated.

When I turn the system on by pressing the power button in the center, it ALWAYS goes to AC and is always in recirculate mode. When it does this, I hear the clutch on the AC compressor engage as normal. I press the AC button to turn it off and also press the recirculate button to turn it off and back to fresh air. I've only owned this car for the last 3 very cold months and haven't needed to use the AC yet but it does this every time we turn the HVAC on. A crazy example was back during the "polar vortex", I started the car after work while the outside temp showed 8 degrees. Turned the heat on and it automatically went to AC in recirculate mode.

Couple of observations to add:

1. When the HVAC is off, I can rotate the power button (for the fan speed settings), this will cause the system to turn on as well and always starts in AC w/ recirculate. I don't know if this is normal, I realize pressing the power button turns it on, but if I rotate the fan speed, it turns on also.

2. If I shut the car down and leave my HVAC in it's current setting (not turning it off), when I restart the car, it will still be in that setting. This eliminates the AC "problem" I'm describing above but also causes cold air to blow out until the coolant warms up. I'd rather leave the system off until the coolant warms up some.

3. I understand that the compressor runs when the front defroster is active, but this is occurs without the defroster being utilized.

4. The radio had a mind of its own when I bought this car. Every time I started the car, it was either playing music, playing a movie or doing something else (even though it was turned off at shutdown). The dealer updated the HMI software per TSB 17-NA-025 (https://www.corvetteactioncenter.com/tech/knowledgebase/print-1326.html) and fixed that problem. The AC was doing this before and after that update.

My previous two XL's were an 07' and an 11', both Denali's. HVAC controls were totally different but behaved as they should. Outside of the labels peeling off the buttons, I had no concerns with the climate control in either of those vehicles.

Any thoughts or suggestions? I'm not using the "auto" feature so my thinking is that the AC should stay off until I turn it on.
 
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inane222

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Thought I would post kind of a follow-up: messed with the climate control settings that are only available while the engine is running. I turned off the auto front and rear defrost setting, just as an experiment. It didn't change anything. Started the vehicle this morning. Temp was 18, Sync was selected, bi-directional vent selected, temp set to "High". When I pressed the power button, the AC light came on and the screen showed that the system was in recirculate mode.

Doing some online research and I ran across pages of forum posts discussing this issue, but they were forum multiple sites dealing with the Chevy Colorado and GMC Canyon. Guys having the same issue. One guy put it very well about cutting the heat on, only to realize several miles down the road you haven't warmed up yet because the AC compressor is running.

Not sure if there is actually a defect here or if this is normal and is simply in the HVAC software. I'm headed to the dealer soon for the ATF flush for the infamous 8 speed shudder. I may run it by them while I have it there.
 

Big Mama

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It sounds like your system defaults to auto mode. Like you I have an 07 Denali. If I keep the system out of auto the ac doesn’t come on but every other time it does especially when I use the remote starter. It doesn’t really make sense for the ac to come on when it’s 32 today but I guess in auto mode it’s set that way.
 

Brandon Hubbard

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Thought I would post kind of a follow-up: messed with the climate control settings that are only available while the engine is running. I turned off the auto front and rear defrost setting, just as an experiment. It didn't change anything. Started the vehicle this morning. Temp was 18, Sync was selected, bi-directional vent selected, temp set to "High". When I pressed the power button, the AC light came on and the screen showed that the system was in recirculate mode.

Doing some online research and I ran across pages of forum posts discussing this issue, but they were forum multiple sites dealing with the Chevy Colorado and GMC Canyon. Guys having the same issue. One guy put it very well about cutting the heat on, only to realize several miles down the road you haven't warmed up yet because the AC compressor is running.

Not sure if there is actually a defect here or if this is normal and is simply in the HVAC software. I'm headed to the dealer soon for the ATF flush for the infamous 8 speed shudder. I may run it by them while I have it there.
I just traded in a 15 Colorado z71 and it did exactly what you said from day 1 with 2 miles on it. My 15 denali is exactly the same. Dealer said that was normal of the Colorado.
 
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inane222

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Thank you guys for the follow up comments.

14 degrees this morning, same results - AC with recirculate. Oddly enough, I popped the hood and the compressor was NOT running, even though the AC light was illuminated on the dash. I'm assuming it won't cut on below a certain temp, but when it's in the mid 30's and above, I can hear the clutch kick in as soon as I turn on the HVAC system.

I believe I''m going to quit letting it drive me crazy and just accept it as "normal" behavior.

Thanks again all.
 

swathdiver

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Thank you guys for the follow up comments.

14 degrees this morning, same results - AC with recirculate. Oddly enough, I popped the hood and the compressor was NOT running, even though the AC light was illuminated on the dash. I'm assuming it won't cut on below a certain temp, but when it's in the mid 30's and above, I can hear the clutch kick in as soon as I turn on the HVAC system.

I believe I''m going to quit letting it drive me crazy and just accept it as "normal" behavior.

Thanks again all.

It is normal and the compressor runs when its cold out to serve as a dehumidifier. In the old days we turned the compressor on and off and same for heat. To get heat, a valve had to open allowing coolant into the heater core. Nowadays, there is heat available all the time and the AC blends the hot and cold together to reach the desired temperature(s) through the actuators.
 

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