AC compressor controlled by dial knob ?

[carplan15]

does the AC compressor turn on when I turn the temperature dial knob to the blue ?

or does the AC comp only turn on when I push the little button ?

a few times lately it seems like even tho I haven't pushed the button to turn on the AC I can hear feel something clanking under the hood that sure sounds like a compressor starting up when I turn the dial knob to blue

And the air feels cooler coming out at first but then driving around the air temp seems to get back ambient vs cooler

 

[MarkS]

Is the defrost mode selected? The AC will run in defrost above a certain temperature.

Otherwise, the AC system remains a mystery to me. For example, does the setting of the temperature knob determine how much the AC compressor cycles on and off?

 

[grayback]

the "little button" turns on the AC compressor. the knob with the blue thing controls the temp. little button turned off (no light), temp knob is useless. it will be on "fan mode" only. same thing with heater.

 

[Maddmatts]

The temp knob only controls how much heat from the the heatercore is added to the air in the vents. It doesn't control the A/C system in any way.

 

[Swordsmith]

The compressor runs if the AC button is on OR if defrost is on (or both). You can run AC and hot, you can run defrost and cold. Results of doing this can be squirrelly but it does run. What you can't do, although I wish you could, is run the defrost (which blows air onto the inside of the windshield) without running the compressor.

The compressor costs you between 2 and 5 mpg, while the heat doesn't cost any measurable mpg at all, so if might be nice to have the option of just heating the window, under some circumstances. On the other hand, the compressor and defrost does do a great job of removing fog from the window, so I would not want to cut it off completely unless I lived in say south florida or some such.

 

[carplan15]

the "little button" turns on the AC compressor. the knob with the blue thing controls the temp. little button turned off (no light), temp knob is useless. it will be on "fan mode" only. same thing with heater.

The temp knob only controls how much heat from the the heatercore is added to the air in the vents. It doesn't control the A/C system in any way.

hmmm.... I tried this again yesterday sitting there with the engine running about 75degrees outside. turning the knob all the way to the right into the blue line put out noticeably cooler air, then turning knob too middle the air temp matched outside, turning knob to the left into the right put out heat. and yes I did this without pushing the ac-button

I will ask dealer about this when I take car in for 6 month checkup, because how can the air be cooler than outside unless the AC compressor is running ?

 

[carplan15]

...I will ask dealer about this when I take car in for 6 month checkup...

dealer says yes - the AC compressor is controlled by the temp knob also the little button also the defrost rotary

 

[MORTIS]

dealer says yes - the AC compressor is controlled by the temp knob also the little button also the defrost rotary

Dealer must be mistaken. They are probably thinking of auto climate control, which the Sonic does not have.

 

[borockster]

On my 2013 RS I can run the defrost without the a/c comp by simply turning the a/c button off.

I'm sure you can as well and you can easily verify this just by watching while someone else pushes the button.

Same is true for the temp knob. While it is true that by selecting a temp range in the blue the a/c comp will kick on you can easily shut it off by hitting the a/c button.

 

[Maddmatts]

Maybe the 2013's and up are different in this regards?

My 2012's A/C will only turn on under two conditions;
1) When I press the A/C button.
2) When I set the vents to either "front-window defrost" or "front-window defrost + floor".