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According to the manual for the 2006 Civic, pressing the windshield defroster button overrides all previous settings and should turn on the A/C. However, I don't find this to be the case. I'm pretty sure it used to be true, but I just had the audio system or stereo trim repaired because the backlighting wouldn't work, and apparently controls were transferred.

A/C works (the button light turns on) when I press the button.

Should pressing the windshield defroster button always cause the A/C to turn on if it was previously off?

 
Rep Power: 309

If it is cold outside the compressor won't kick in.

And even if the system is set so you can release the A/C light it will still light each time it is selected,then it can be released.

 
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I'm still not sure about proper behavior: if I depress the windshield defroster button, should the A/C light come on under all circumstances? (I understand that it can be turned off). When I depress the windshield defroster button, the A/C light never turns on automatically.

 
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On the 8th gens I cannot say, On my 7th gen any time I go from floor (only) to floor/def or def then the light turns on.

Do you remember how it acted before the work was done ?

 
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Not sure, but I think it worked. Can an 8th gen owner weigh in here?

 
Rep Power: 813

you are talking about the actual rear defrost button for the window heater lines and not the front window defrost air vent setting right? in which case, a/c should never come on. the defrost system does use a ton of power tho. at first i thought the a/c came on silently (without the light coming on), but i couldnt actually hear the compressor. when in doubt, open the hood and see if you hear the compressor click on. i really do not see why it would need to turn on tho, since rear defrost has nothing to do with the a/c system. now if youre talking about the dial setting for front window vent defrost, then yes the a/c light should always come on, and there is a special code you can do to have control over it so you can turn it off. also remember, just because the a/c light comes on, does not mean the compresor is working. it has a pressure switch lockout and usually will prevent compressor function below freezing temps.

 
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No, I'm talking about the windshield defrost air vent setting.


Well, that's a problem, because the a/c light doesn't come on. The special code wouldn't prevent the light from coming on, would it?

More importantly, what could be causing this problem? As I wrote, if I press the A/C button manually, it will light.

 
Rep Power: 813

no, the special code allows you to turn off the a/c once it turns on. it should still come on all the time by default. without the code, there is no way to turn it off once it comes on. a few guys here with 8thgens said the same thing and they did the code so they could switch off the a/c after switching to defrost mode. i have no idea why its happening, but really is it a big deal? i mean, if you push the a/c button and it works, then i wouldnt worry. i would actually prefer it to be like your setup, so i dont have the a/c compressor running for 2 seconds before i switch it off again.

 
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Doesn't one want the a/c to turn on automatically most of the time?

 
Rep Power: 813

nah, uses too much hp and voltage.