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I was wondering... A conventional ICE car can mix in heater core diverted air in order to obtain a desired automatic temperature in the cabin. But how does the auto-A/C function work on the Volt (assuming the ICE isn't running)? Surely it doesn't use the resistance heater. Is the electric A/C truly a variable output system?
 

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The AC system in volt is electrically driven and variable, from about 500W up to 3000W (? IIRC).
It will also just shut off and cycle as required.
 

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The Volt and most hybrids have the A/C compressor decoupled from the gas engine (which will not be running all the time), and most are powered from the traction battery directly through a temperature controlled relay or the system controller. Open the hood of the Volt or any hybrid (domestic or imported) and you will see a set of orange cables going to the compressor. That is the clue that it is powere by a much higher DC voltage than 12 VDC.

And you may now notice that hybrids have very little or no accessories powered by the engine crankshaft anymore and may have no belts. The ICE will disappear soon, as BEVs take over the ICEVs, and every EV will have the same accessories but electrically powered.
 

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But how does the auto-A/C function work on the Volt (assuming the ICE isn't running)? Surely it doesn't use the resistance heater. Is the electric A/C truly a variable output system?
As others have said, AC is fully electric and will cycle on/off as needed. Love it!!

The Volt does use electric resistance heat when the ICE isn't running and you need heat. Engine Running Due to Temperature (ERDTT) will kick in to run the engine to generate heat when it gets really cold - but that is a much debated "feature" around these parts. The will use the A/C to pull moisture out when the heater is running, but no heater use when you need cooling.
 

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I was wondering... A conventional ICE car can mix in heater core diverted air in order to obtain a desired automatic temperature in the cabin. But how does the auto-A/C function work on the Volt (assuming the ICE isn't running)? Surely it doesn't use the resistance heater. Is the electric A/C truly a variable output system?
It works the same as your home A/C System. It cycles the A/C on and off as needed.
 

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It works the same as your home A/C System. It cycles the A/C on and off as needed.
Plus resistance heat if needed. The A/C is not a heat pump.
 

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If you have auto-defog set, it will use heat in the summer.
I have never noticed the resistance heat being used to defog in the summer. Only de-humidified A/C air. And there is usually plenty of warmer air available from outside the car.
 

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Plus resistance heat if needed. The A/C is not a heat pump.
Your comment made me wonder... In most cars defogging is accomplished by first passing the air through the A/C evaporator. This cools the air, of course, and since cool air won't hold as much water vapour it condenses out (which is why you see water condensing on the outside of a cool glass).

After the dried air leaves the A/C evaporator, it's passed through the heater core to warm it up - because warm air can hold more water vapor than cold. Therefore, when this warm, dry air passes across the windshield it readily absorbs any moisture on it.

So what I'm wondering is this: in a pure electric vehicle that only has a heat pump (not the Volt, but perhaps something like a Leaf), and if that same heat pump is used for both warming and cooling the air, how does defogging work? It can't warm and cool at the same time. Does it just heat the air like some older ICE cars I owned that didn't have air conditioners? Does it just cool the air? In either case, the resulting air would be either dry but cold or warm but moist, neither of which seem to me like it would be as effective. One of the things I really, really appreciated about my first A/C-equipped car was how much more effective the defogger was.
 

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I have never noticed the resistance heat being used to defog in the summer. Only de-humidified A/C air. And there is usually plenty of warmer air available from outside the car.
It does during summer in New Hampshire. I usually keep the system on auto Eco with the temp set to 75. On cold rainy mornings, outside temp in the lower 50's, if I change climate to fan only and forget to lower the temp from 75, the heater will run during de-fog.

I like de-fog on because I consider it a safety feature.
 

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It does during summer in New Hampshire. I usually keep the system on auto Eco with the temp set to 75. On cold rainy mornings, outside temp in the lower 50's, if I change climate to fan only and forget to lower the temp from 75, the heater will run during de-fog.

I like de-fog on because I consider it a safety feature.
And this car is tight when the recirc is (auto-)on. It doesn't take a lot of temperature difference between inside and outside for fogging to start.
 

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In either case, the resulting air would be either dry but cold or warm but moist, neither of which seem to me like it would be as effective.
Just air on the windshield of any temp is very effective at keeping fogging away.
On spring/fall nights when it's just starting to fog up, turning fan on notch 1-2 without any AC or heat will keep the fogging at bay.
Add in AC drying the air out and even better.

You need to keep your windshield clean, too. A dirty windshield, there's no hope.
 

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Just air on the windshield of any temp is very effective at keeping fogging away.
Out here in the Left Coast rainforest "air of any temp" really doesn't cut it. When it's pouring out and the car is cold and you get in with a soaking wet coat, it takes a *LOT* of defogging power to clear the windshield. That's where I've found the combination of A/C and heat to blast warm dry air at it makes a huge difference.

Which I why I wonder how effective an HVAC system with just a heat pump would be at defogging...
 
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