[rhudeboye]

I would assume modern cars run more efficiently with the AC off as it’s able to pull heat from the engine. But whenever I turn on the heat, the car switches on the AC. I have to then shut it off manually. But I was wondering if the climate control makes efficient use of the compressor and cycles it, somehow making it more efficient. IDK.. Any thoughts?

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[flash]

the ac should not kick on when in heat mode. i wonder if your cabin temp sensor is not working.

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[tamathumper]

As I understand it, lots of cars turn on the A/C compressor when in "defrost" mode, supposedly to dry the air and prevent fogging.



I can say I've read it in at least one of my Owner's Manuals (Ford) and verified it with a brief Google search for "ac compressor defrost". If it's on the Internet, it *must* be true, right!? <img src="/forum/images/smilies/968/biggrin.png" class="smilie" alt="" />



Is yours also coming on when in "dashboard" or "vent" mode? (I don't know what else to call that) <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />

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[lbpesq]

How, specifically, are you "turning on the heat"?

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[rhudeboye]

[quote name='lbpesq' timestamp='1329185941' post='121809']

How, specifically, are you "turning on the heat"?

[/quote]



I notice it when i hit "Auto" (the temp is currently set to 77) but it also happens when i use the touch screen and set the fan speed. The little AC light keeps coming on and I have to switch it off.

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[rhudeboye]

[quote name='tamathumper' timestamp='1329181366' post='121807']

As I understand it, lots of cars turn on the A/C compressor when in "defrost" mode, supposedly to dry the air and prevent fogging.



Is yours also coming on when in "dashboard" or "vent" mode? [/quote]



In auto it decides how to direct the air and it changes according to zone temps. I've observed it often using a mix at first.

Drying out the air makes sense but on mornings when its 30 degrees out... IDK

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[rxter]

"I notice it when i hit "Auto" (the temp is currently set to 77) but it also happens when i use the touch screen and set the fan speed. The little AC light keeps coming on and I have to switch it off."



Clearly you are speaking of the Lexus, or my 968 touch screen has been on the fritz...



Same thing happens on Auto in our 2002 Honda. Stupid. I've heard that they do that to get cycles onto the compressor in the winter so that it stays lubed - who knows? Sounds like more idiot proofing to me.

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[rhudeboye]

[quote name='rxter' timestamp='1329240073' post='121823']



Clearly you are speaking of the Lexus, or my 968 touch screen has been on the fritz...

[/quote]



<img src="/forum/images/smilies/968/laugh.png" class="smilie" alt="" /> <img src="/forum/images/smilies/968/laugh.png" class="smilie" alt="" /> yeah, the Lexus.



I was told the following:

The thought is "THE HUMAN" will fog up the glass, so the AC is used as a Dehumidifier.



Also, it's efficient enough not to decrease your MPG much. The AC operates on low. If you want faster defog, turn on the Defog. It will pump the AC to high and the fan to high to clear up the glass in a few seconds.



So Thumper was right.

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[94SilverCab]

Rhude,



Time to join GS450hForums.com <img src="/forum/images/smilies/968/glare.gif" class="smilie" alt="" />



Jay

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[lbpesq]

Oh, the Lexus! I was confused as my 968 has no "touch screen".

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[rhudeboye]

[quote name='94SilverCab' timestamp='1329251753' post='121828']

Rhude,



Time to join GS450hForums.com <img src="/forum/images/smilies/968/glare.gif" class="smilie" alt="" />



Jay

[/quote]

yup, thats where I got my answer. But you guys all own newer cars as well as your 68s. So i figured I'd post here. Not to mention, going outside of this forum is something i avoid as much as possible. <img src="/forum/images/smilies/968/closedeyes.gif" class="smilie" alt="" />

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[Scott Collins]

A/C works great to dehumidify, hot or cold.

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