My first winter with my '16. If the climate control is on auto, AC is always on. Why? It can be 20 degrees outside, and AC is on. Now I understand you want some AC to get rid of interior fogging, but always on? It's supposed to do this, right???

 

It’s normal. The A/C compressor will only cycle on when needed to cool or dehumidify. It’s actually good for the A/C system and will help keep compressor seals from drying out as well.

 

^^Exactly this but a good question OP!

 

Yup, what they said ^^^ My Chevy truck does the same thing.

 

I think I did read somewhere that there is a temperature below which the compressor will not come on but it maybe very low, like zero degrees.

 

If you turn the fan off the AC is off. I do that when we get cooler weather and the windows are down and the top's off or I'm at the drag strip.

 

Just because the AC annunciator light is on does NOT mean the compressor is or will be engaged. It just indicates that it is part of auto mode and will turn on under the correct conditions: Call for compressor activation by the climate control system AND outside temperature high enough for safe compressor operation.

At least with the Corvette you can de-select it easily with a button if you just want ventilation but with my Cadillac ATS I have to choose climate from the infotainment menu to get into the additional controls to lock out AC operation.

 

Also, on our 2017 the default mode for air source is Recirc instead of Outside. Turning off Recirc also takes it out of Auto.

I suspect that's because outside air will pull in the heat and possible fumes from the hood air exit, but just speculating.

 

I'm still trying to figure out my CTS system...don't understand why they make so difficult. I have yet to even look into this on the 7....

 

 

Let's do an experiment:
Start car and wait a few minutes or just drive it a while, with the system in Auto.
(Pull over for safety if driving)
Adjust the temperature up or down by just one degree, don't adjust anything else. That will open the HVAV window on the screen, for a few seconds.
Look at what the picture shows for air source. On ours it will show Recirc, and the Auto light will be on. We tried that on one other C7 (don't recall the year) and it worked the same.

We can each try to experiment on other cars, but that's going to be slow going for me because most Corvettes around here are parked for the winter.

 

The Chevrolet setup is much more driver friendly and has real controls for often used HVAC and audio system buttons instead of forcing almost everything to be done through the CUE screen or panel touch controls.

Cadillac has been trying to be more European for a number of years now and although they missed a lot of the good things out of Europe they did manage to mimic the poor user interface found in some of the offerings from Europe. It is a good thing my ATS has a heated steering wheel because it is just about impossible to operate with gloves unless you are using the special (and not very warm) type intended for use with smartphones.

CUE has improved since 2014 but it still isn't great. In my 2014 ATS the backup camera sometimes delays for a couple of seconds when shifting into reverse making it all but useless and last week I had the nav system on and as I was backing out of a parking lot it temporarily shifted from the rear view camera mode to showing a screen that it was loading the map. Apparently CUE was designed as part of a junior high school vocational learning class.

 

They don't run the compressor all the time even when it is hot outside. However, when the air temp drops into the high 30s to low 40s there is a chance the evaporator will freeze over so they don't run the compressor when the air temp in the evaporator drops below 38 degrees. I got that temperature directly from the GM Factory Service Manual for my 15 C7.

Bill

 

True but when you put the defrost on, on a cold day or snowy with heat the compressor comes on.

 

Dang, that's what I wanted to say.

 

In addition to the evaporator temperature limit Bill mentioned the compressor is also inhibited when the outside temperature drops a little below freezing and this is to prevent compressor damage. You cannot compress a liquid and operation in too low of an ambient temperature will cause this undesired action which is why the compressor will not run when outside temperature drops too low; this is a protective feature of the system. Just because the light is on doesn't mean the compressor clutch is (or can be) engaged. It will operate in lower temperatures when recirc or defrost operation is requested as long as the outside temperature is high enough to avoid damage to the compressor.


Car AC systems are designed for safe AC operation at much lower ambient temperature than household units because they are needed to help with defogging however there is a limit to how low they can go without adding heat strips to prevent the refrigerant from remaining in a liquid state at the compression phase of the cycle. These extra heat sources are too expensive and complex to bother with in most vehicle systems. Seldom is there a need to remove moisture from the air in cars via the AC when it is extremely cold and defeating/preventing recirculation is done by most automotive systems once it is too cold to run the AC compressor and this also prevents interior surface fogging.

AC compressors don't like trying to compress liquids any more than your engine does although usually the result is a little less spectacular than a windowed block.

 

After two weeks on my first Corvette, I am still learning the Corvette systems, but for cold weather ops in my Mustang GT, the manual recommends the A/C be used to control humidity for defrost/defog.
Since the 'vette has the option to automate the defog/defrost functions, I assume the 'vette's A/C would be activated for the same reason.

 

Interesting. Good catch. The window says Auto/Recirc but the Recirc button isn't lit. If I push the Recirc button then the Auto light goes off.
It looks like Recirc is the default without lighting the Recirc button?

 

Great post, I was wondering this myself.

 

Just press the temperature readout on the screen and it will momentarily show the AC settings , no need to adjust the tem to do this.