Two week old car, air conditioner blows cold air just fine, sort of. If I set controls on “auto”, the air coming out of vents is cool, not cold. If I select AC along with “auto”, extremely cold air. Manual says I should be able to just set to auto and forget it. Anyone else experience this?
thanks.

 

Auto mode should not generate extremely cold air, it should provide cold air sufficient enough to maintain the set temperature. If it's too cold it would drop below your set temperature too quickly. There is usually a "Max AC" mode which is like a "cool me off as soon as possible mode". I wouldn't be too concerned about how cold the air feels, unless the system is unable to keep your set temperature within a reasonable amount of time. Maybe it takes 5 minutes to reach 74, or maybe it takes 10 minutes; however it should be able to maintain your 74 set temperature. If it doesn't, then there is a problem.

 

It depends on the difference between the temperature you’ve set it to and the temperature it’s measuring in the car. Set the temperature low enough it will blow cold air, but as the temp starts dropping it will become less cold.

 

what you posted is what I would expect. I live in Fl, car garage kept, temp set to 73, both sides synced. Air feels warm and humid. Will have it looked at when at the dealer when I go,for first oil change. Thanks!

 

I will,try with temp at lowest and see if that has any effect. Thanks!

 

I found this the case, AC isn't on using AUTO until you push the AC button. Last I tried it was earlier in the season when it wasn't as hot, so maybe I'll test it again.

Manual says: Automatic Operation
The system automatically controls the fan
speed, air delivery, air conditioning, and
recirculation to heat or cool the vehicle to
the desired temperature.
When AUTO is pressed, all four functions
operate automatically. Each function can
also be manually set and the setting is
displayed. Functions not manually set will
continue to be automatically controlled,
even if the AUTO indicator is not lit.

A/C : Press to turn the air conditioning on
or off. An indicator light comes on to show
that the air conditioning is enabled. If the
fan is turned off, the air conditioner will not
run. The A/C light will stay on even if the
outside temperatures are below freezing.
If the A/C is turned off, the air temperature
coming through the climate control system
may be warmer than the ambient
temperature. It is recommended to use auto
climate control to maintain comfort.

 

It shouldn't because you don't want to cool the cabin temperature too quickly without removing the humidity. The system should be working to both cool the temperature as well as remove humidity. It can't remove humidly if it cools down the cabin too quicky so even though you set the temperature really low, that should not affect the temperature coming out of the vents.. It will just continue cooling to your lower set temperature.

 

thanks! That’s the way mine is working, but the manual says you just need auto

Automatic Operation
The system automatically controls the fan speed, air delivery, air conditioning, and recirculation to heat or cool the vehicle to the desired temperature.
Air Delivery Mode Control : Press Y, [, or z to change the direction of the airflow.
Any combination of the three controls can be selected. An indicator light comes on in the selected mode button.
When AUTO is pressed, all four functions operate automatically. Each function can also be manually set and the setting is displayed. Functions not manually set will continue to be automatically controlled, even if the AUTO indicator is not lit.

 

Are people really suggesting that the A/C only runs if the A/C button is manually pressed? This is absolutely not the case. I have never once pressed the A/C button manually.

 

You should be able to press Auto, set the temperature, and go.

When you press Auto, either on the screen or on the row of buttons (doesn't matter), that should return all functions to automatic (fan speed, air conditioning compressor (A/C), as well as air delivery, and recirculation to heat/cool the car to the temp you have set. You should be able to set the temperature and go. The A/C button should be lit. If you touch any of the other controls, you own them. So if you adjust fan speed, then you own it. The purpose of the A/C button is to disable the air conditioning compressor. If you press it, then you own that feature. But if you press Auto again, it will return all settings to automatic control. If you are pressing Auto, and not seeing it light up the A/C button, then something is wrong.

I tested all of this before writing it. Pushing Auto returns all the features to auto. pushing A/C will disable the compressor. pushing auto again turns the compressor back on. Same with the fan speed.

As for temperature coming from the vents - for years and years - back to at least 1965 if not earlier, GM has designed their climate control systems so that the compressor is on almost all the time. All air flows over the A/C evaporator in the car, cooling and dehumidifying the air. Then a portion of the air flows over the heater core - and a portion does not - and the air mixed before exiting the into the cabin. The result is dehumidified air at the correct temperature. For a quick cool down, the air is not reheated, and the fan speed will be high. The air will be very cold coming out of the vents. As the cabin temp approaches the target temp, the air from the vents will not be as cold, and the fan speed will slow down. The system will regulate to maintain the desired cabin temp and keep the fan speed as low/quiet as it can be.

Some other design in the old days would just cycle the compressor on and off to regulate the temperature.

 

The A/C should engage based solely on the temperate setting automatically. The A/C button is either a Max A/C mode (forget about humidity -- I need cold air or I'm going to pass out! -- blast me!) Or the A/C button lets you turn on the A/C when the system is actually heating. If it's cold and humid, it's beneficial to keep warm with cabin heat, and also run the A/C to extract moisture. That's what the A/C button should be used for.

 

In my 2021, if I push Auto, the A/C is on and the A/C lit is on and the compressor is running. The compressor should run almost all the time in Auto. The manual says the A/C light will stay on even in freezing weather. The manual recommends leaving the car in the Auto mode and not turning the A/C off. Also, when I start my car, it comes up all the climate control settings as they were when it was shut off - so it is in Auto mode, and the A/C is on, button is lit. I have never touched the A/C button before today when I tested it after reading this post.

"Automatic Operation
The system automatically controls the fan speed, air delivery, air conditioning, and recirculation to heat or cool the vehicle to the desired temperature.
When AUTO is pressed, all four functions operate automatically. Each function can also be manually set and the setting is displayed. Functions not manually set will continue to be automatically controlled, even if the AUTO indicator is not lit. For automatic operation:
1. Press AUTO.
2. Set the temperature. Allow the system
time to stabilize. Adjust the temperature
as needed for best comfort.


A/C : Press to turn the air conditioning on or off. An indicator light comes on to show that the air conditioning is enabled. If the fan is turned off, the air conditioner will not run. The A/C light will stay on even if the outside temperatures are below freezing. If the A/C is turned off, the air temperature coming through the climate control system may be warmer than the ambient temperature. It is recommended to use auto climate control to maintain comfort."

 

I agree with @Andybump. My climate control and A/C function just like he describes his does, just in case the quotes from the owner’s manual wasn’t enough.

 

Appreciate everyone’s input. Thanks

 

Attached is an illustration of how I believe the GM HVAC systems regulate temperature. The temperature is not primarily regulated by turning the compressor on and off, nor is it primarily regulated by adjusting the flow of hot coolant through the heater core. Rather, they are almost always on, and temperature door(s} are used to control the mix of cool air, and reheated air. This provides for air that is always dry, which aids in keeping the interior windows clear, even in cooler weather. The real systems are more complex of course, having individual controls for driver and passenger. The service manual mentions both a Left Temperature Door and a Right Temperature Door, and there are scan tool parameters that indicate their respective commanded positions. It also mentions left and right heater cores. Sometimes the scan tool parameters are generic - and may include references to features not actually in the car. I do not believe the C8 actually has two two heater cores. It only refers to one replacement procedure for a heater core. And, the illustration of the cooling system shows only one heater core. But we do know that the car allow for separate setting of the temperature for the driver and passenger.

Most of this detail does not appear in the version of the Service Manual that I have, but here is a line from that manual that mentions the HVAC temperature door: "The amount of heat delivered to the passenger compartment is controlled by opening or closing the HVAC module air temperature door." I am familiar with the basic principles of this design having disassembled and repaired the Automatic Climate Control temperature control door in another GM vehicle.

While I was looking this up, I ran across something called a Front Floor Console Auxiliary Cooling (K4C). K4C is the code for the portable wireless device charger. Apparently that requires some cooling air. I attached an image showing the duct location. The complexity of this car has no end.