A/c Light And Button

[stepper459]

I have a 2001 GMC Yukon XL (SLT, 5.3, 4x4, if any of that matters) and lastnight, it was 36 degrees and foggy, and I was getting fog on th inside of the windows. So I hit the a/c button, and it flashed and then wouldn't turn on. so I pushed it again and same thing. but I could then smell a/c and the windows defogged like it was on. So I tried turning the air switch down to just feet, (in case it was something about being on defrost) and same deal. But then I got in the car this afternoon and noticed that the a/c light was on (!) even though I hadn't pushed it recently, at least not since I turned the car off lastnight. WTF!

1. Why does it do this?

2. How can I tell if a/c is on, if it appears to be on even when the light is off?

3. What does the flashing light indicate?

4. Is this normal or totally whacky?

 

Thanks!

 

Morgan

[dreman]

I think it's because the outside temp was so low. The AC will not come on below a certain temp. When you got in later that afternoon, it had warmed up, and the AC would finally come on.

 

The windows defrosted anywaybecause it was cold enough to work anyway. The AC only comes on when it's a little warmer to chill the air to take the moisture out so it will defrost faster. Air that is already cold doesn't need the AC to come on for defrost.

[Draenor]

I think it's because the outside temp was so low. The AC will not come on below a certain temp. When you got in later that afternoon, it had warmed up, and the AC would finally come on.

 

The windows defrosted anywaybecause it was cold enough to work anyway. The AC only comes on when it's a little warmer to chill the air to take the moisture out so it will defrost faster. Air that is already cold doesn't need the AC to come on for defrost.

I've heard the same. I never experienced it as it doesnt get cold enough down here.

[minibike132]

Have you checked the owners manual. I only have access to 03 and up but 03 with auto states if it is too cold out and the ac button is pressed it will flash 3 times to let you know it's too cold out. If it is cold out ac operation is inhibited to protect the system. You shouldn't need to use the ac button in any GM to defog windows. With the selector in defog it will turn on the ac automatically to help as long as it's not too cold.

[d3athsong]

This may sound like a stupid question, but why would you crank the cold to defog your windows?

[stepper459]

it's not taht I want the cold, but rather just the moisture-removing properties of the a/c. My old Honda Accord had a totally separate button for a/c and in the winter when the windows would be foggy I would put on the a/c with full heat, and it would help tremendously with the defogging - not deFROSTing - but liquid condensation.

here's what's weird: in the summer, I remember it would flash like that if I set the directional control even one notch past the vent/feet mode (toward feet/defrost), but if I turned it back, it would let the light turn on if I pressed the button. This indicated to me that a/c was automatically engaged in defrost mode no matter what you did (which makes some sense) and that the light just wouldn't come on because it's almost redundant. What gets me is lastnight, I would be driving along and notice the fog creeping down the windows, and without changing anything except pressing the a/c button a few times, the windows would "magically" defog, exactly as if I just turned on the a/c and i could smell the a/c (that distinct smell when it hasn't been on in a while). Maybe the auto-a/c actuator for defrost mode isn't working? and pressing the button a few times "wakes it up"? Or is that crazy

[minibike132]

I don't think he said he cranked the cold just turned on ac. The ac helps dry out the air thats the major thing it's doing when making you feel cooler in the summer. GM ac comes on auto in defog. Lots of imports don't and you need to manually turn it on.Ever see a honda in the winter with the windows totally fogged up, That person didn't know to turn on the ac.

[minibike132]

I think it's because the outside temp was so low. The AC will not come on below a certain temp. When you got in later that afternoon, it had warmed up, and the AC would finally come on.

 

The windows defrosted anywaybecause it was cold enough to work anyway. The AC only comes on when it's a little warmer to chill the air to take the moisture out so it will defrost faster. Air that is already cold doesn't need the AC to come on for defrost.

 

 

yea what he said, you must type faster than me.

[minibike132]

this is confusing were all typing at the same time and answering ? that havent been posted yet.

[minibike132]

OK well I need to get back to work, If this isn't answered after work I'll come back.

[stepper459]

I think I understand, i guess I just expected the little indicator light to be on whenever the a/c is on, but I can accept a little weird behavior - as long as the windows get cleared, which they do, eventually.