A/C in cold weather?

I've heard that car A/C doesn't work below a certain temperature because if it's freezing out, the coils might freeze up. Yet the guy at the dealer says, run the A/C to clear interior fog on the windows,
and doesn't make any exception for freezing weather. Could someone explain what actually happens?
If the A/C doesn't kick in when it is freezing out, how come the A/C light still lights up?
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Gordon Zola wrote:

Don't know much about A/C's, but I'm pretty sure that the operating temperature is not at 0 deg C. The coils aren't filled with water, they're some type of liquid similar to freon. According to a website I found, the freezing point of freon-12 is -158C. Maybe some other fluids/lubricants would cause the A/C to seize before the coils would.
http://webphysics.iupui.edu/webscience/physics_archive/refrigerators.html
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A/C works just fine in cold weather.

The light comes on because the A/C is turned on.
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On Tue, 15 Nov 2005 11:39:44 GMT, "Brian Smith"

The AC will turn on at any temperature but won't cool if the ambient temp is below around 5 C. At such low temperatures, the evaporator would cool below 0 C and the water condensing on it would form ice.
Under cold conditions, the AC is useless for dehumidifying the air and preventing fog on the windows.
While the main purpose of AC is to cool the vehicle in the summer, it can be used in the winter to help warm it up. That's because the AC puts a load on the engine, which then warms up faster, and that gives quicker heat out of the heater. Of course this uses up more gas, so turn off the AC when the interior is warm enough.
Randy
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It's not used to cool the air in the passenger compartment it is used to remove the moisture in the air. It does that just fine in my vehicle here in Nova Scotia through Winter.

Apparently not true with my experiences.

Driving the vehicle puts more load on the engine that the A/C ever would or could.
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On Thu, 17 Nov 2005 09:31:36 GMT, "Brian Smith"

Such is the power of faith.

Yes, very true.
Randy
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What in the world are you trying to say? That actual experiences don't mean anything to you?
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That and the fact the reason they say to run the A/C to clear the windows is that it acts like a dehumidifier and helps remove moisture from the air.

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On Tue, 15 Nov 2005 11:51:45 GMT, "Ross Cranford"

Yeah. So in the summer time, the evaporator runs at around 32F/0C, the water vapor in the air condenses on the evaporator coils, forms liquid, and drips out of the car.
But in the winter when it is say 0F/-18C, the water vapor turns to frost on the evaporator coils. It can't drip out because it is solid ice. The evaporator ices up. At least this will be true when the car is first started if the A/C is on.
Ten or 15 minutes later when the interior warms up, the situation may be different, but by then you won't need the A/C to dry the air, because the dry air from the outside plus the heat is doing that.
Just trying to understand what is happening....
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You are listening to people living in the past. While it use to be true that the A/C wouldn't come on at low temperatures it is not true today.

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Gordon Zola wrote:

-----------------------
The best dehumidifier in winter is to turn OFF the recirculate, and pump bone-dry air into your car, displacing the moisture from your wet floor mats. Works best in areas where winter is DRY.
Your Owner's Manual says you should use the AC occasionally in the winter to keep it lubed. It will only cut in above a certain under-hood temperature.
'Curly'
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