Thread: AC compressor runs in heat modes on HVAC

Weird, I've driven a LOT of Impalas since 05' or so and never noticed it, then again I don't care the're rental cars. I'm just glad I can tap a button to turn the compressor on or off.

It doesnt matter if you have the compressor on or off. If you have the heat on with the defrost on, the ac compressor will turn on no matter what. You can't shut it "off" because it's already off in reality and just running because you have it set to defrost. Changing to vent or floor will not have it active.

05' you can....

No you can't it on because you requested the defrost

If you hit the button to shut it off, you are disabling the "defrost" feature that uses the compressor.

Not trying to argue anything but true, you could shut it off but now it's just blowing air.

Just because the ac button isn't lit doesn't mean the compressor isn't engaging. It does, it's automatic.

yes compressor will turn on even with ac button off

its been like that since the HVAC systems became computer controlled "auto climate control" and looks at outside temp (some "save" several days of temp readings as a way to detect season/climate...cross referencing the PCM's IAT sensor and even the BARO sensor, on the data bus in alot of cases), desired temp, settings to control everything, it knows more than you do, do not second guess your computer overlords.

it can tell the conditions likely to result in fogging of windows and takes action to correct it unless your ac is broken.

its actually the colder it gets that the compressor is less likely to be triggered on as the cold air is typically dry and moisture free.

if you dont like a computer controlling things for you...might i suggest that you swap over to the old analog/non digital HVAC.....those are just on/off functionality, no computer thats smarter than you see?

to clarify the anolog system....on/off functionality...it will turn on the AC when you go to the two defrost settings, but then you can push the button and turn it off. when you do this to the digital system, it tells you to ****off, it knows what its doing

Wow I didn't expect this thread to get this much attention.

I pulled the relay for now to test and stuck it in the center console. Takes 2 minutes to put it back in if needed.

For what it's worth, this car has the manual climate control and even one 100% floor mode cycles the compressor. Defrost modes make sense, that's how just about every car I've had was. But the 04' is one of the newest too.

yeah your controls are still computer controlled. you need the analog systems from the 99 and older cars. the ones that have a vacuum line for the control valves

I'm just going to leave this here since you think you're saving yourself some money but aren't.
http://www.classicautoair.com/techta...frigerant.html

Originally Posted by Turbocharged400sbc

to clarify the anolog system....on/off functionality...it will turn on the AC when you go to the two defrost settings, but then you can push the button and turn it off. when you do this to the digital system, it tells you to ****off, it knows what its doing

I'm not sure this is directed at me, but I do have I guess what you would call the analog system, for this car but its entirely electronic. I tried it again today as until this weekend my AC button has been stuck on since a few months after I got the car. Well since I live where it feels as though it's the edge of a volcano I didn't try to fix it. Now that it's sooo cold now that it's in the 50's I decided to fix it. I had used the button a few times over the weekend and checked it and sure enough you ask for defrost and the compressor comes on along with the fans.

Jeff