XLR82XS
D M C
EXACTLY. It's great to have AUTO and there's a reason vehicles today have that feature in climate control systems. Set your desired temperature and go.
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HVAC question. What does "AUTO" do?
- Thread starter Garlan Garner
- Start date
Last edited:
Auto gets the cabin to the desired temperature... eventually.
It maintains the cabin at that temperature... somehow.
And most of the time it works.... reasonably well.
You'd think that the greater the temperature differential, the higher the fan speed. But it isn't always like that. My 2 previous cars they both had an OPTION of imposing manual fan control on top of the automatic temperature setting, which sometimes was necessary, because getting into a really hot cabin sometimes the fan was barely wheezing; or when the car is already chill, the AC decides to blast an arctic storm.
But for the most part auto climate control in most cars work well.
Though my favorite system was this Honda. All the controls were literally at my finger tips with hands in the standard driving position. The cabin was small so extremely easy to bring to temperature. And the 7 stage fan allowed you to set just the perfect speed.
It maintains the cabin at that temperature... somehow.
And most of the time it works.... reasonably well.
You'd think that the greater the temperature differential, the higher the fan speed. But it isn't always like that. My 2 previous cars they both had an OPTION of imposing manual fan control on top of the automatic temperature setting, which sometimes was necessary, because getting into a really hot cabin sometimes the fan was barely wheezing; or when the car is already chill, the AC decides to blast an arctic storm.
But for the most part auto climate control in most cars work well.
Though my favorite system was this Honda. All the controls were literally at my finger tips with hands in the standard driving position. The cabin was small so extremely easy to bring to temperature. And the 7 stage fan allowed you to set just the perfect speed.
DopeGhoti
Active Member
Yes, A/C creates cold coils, those cold coils remove heat from the air, and remove humidity since the moisture will condense on the coils and drip out the bottom of the car.
Many (maybe even most) "auto" HVAC systems in cars will run the A/C all the time, regardless of what you want the temperature set to. This is to keep the moisture level down and keep your windows from fogging up. It uses a small amount of power, of course, and you have to decide if you're ok with that or not. You can push the A/C button and turn it off if you don't want it.
I think manufacturers do it mainly to prevent quick fog-ups of your windows and people fumbling for defrost controls. They just keep the car de-fogged the whole time and the world is a (bit) safer.
Yes, I'm sure most people on this forum are smart/alert enough to be able to manually use a defrost button. However, given the fact that I see 2-3 cars each night driving up I-15 in SoCal with their headlights off, I also have to admit that too many drivers are clueless.
FWIW, air conditioners are just heat pumps. They just move heat from one zone and pump it to another zone (in the case of a car, from inside the car to outside the car). There are systems (like in RV's for example), that can run in reverse and bring heat into the cabin. The refrigerant (Freon), is just the medium used to transport the heat, it doesn't care if you're trying to make something colder or hotter, or which direction its going.
There are some pretty nice voice controls that relate to the A/C system in the latest software version. I haven't tried them yet, but they look like a way to customize the "Auto" setting a bit. There's a whole list of them in the Voice Commands thread, but here's a quick one to try out: "My feet are cold."
I do like the Auto setting for the most part, but keep in mind that the heater takes a lot of energy; it's best to heat up the seats first, then if you still need more heat, supplement it with the car's heater.
I do like the Auto setting for the most part, but keep in mind that the heater takes a lot of energy; it's best to heat up the seats first, then if you still need more heat, supplement it with the car's heater.
Eno Deb
Active Member
I wonder how much that really is in an EV, given that heating up the air causes significant battery load and then you spend some more energy to partially cool it down again before it reaches the cabin.
Uncle Paul
Well-Known Member
Manual allows driver to control all feature. Auto lets the computer control the features. Both end up with comfy interiors, but auto takes no fiddling.
Example is that when it is cold, turning up the temp manually while keeping the fan on low will take longer than using automatic that will turn the fan up higher to speed warming, then reduce fan speed when warmed to reduce noise.
Owners are always free to use the system they prefer. As OP noted, using automatic will sometimes use more juice that manually if turned way down. Charging times will increase.
The superchargers will also automatically warm or cool your battery to optimize charging times.
Lots going on, behind the scenes, in our vehicles.
Example is that when it is cold, turning up the temp manually while keeping the fan on low will take longer than using automatic that will turn the fan up higher to speed warming, then reduce fan speed when warmed to reduce noise.
Owners are always free to use the system they prefer. As OP noted, using automatic will sometimes use more juice that manually if turned way down. Charging times will increase.
The superchargers will also automatically warm or cool your battery to optimize charging times.
Lots going on, behind the scenes, in our vehicles.
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Auto works pretty good for me but in the winter yeah once it hits the temp it starts blowing cold air which is pretty bad in winter in my opinion. My solution is to move all the venting so it doesn't hit my face or feet or hands. That way it controls the cars temp without hitting me as much with cold air.
XLR82XS
D M C
DopeGhoti
Active Member
And dry air, because it is not suffused with water, takes less energy to heat or cool. Water has a comically high Specific Heat (think of it as thermal inertia)- once you pull it out of the air it's more readily able to absorb either warmth or coolth.
here's everything I've observed with AUTO operation:
IN COLD WEATHER:
- when the cabin is freezing and you set the temp to your desired temp, say, 72F, auto is smart enough not to blast the fan speed until the resistance heating elements are somewhat warm. Then it starts to increase fan speed.
- it is also smart about what percentage to vent from your feet vs face vs windshield, and the proportions will change depending on the difference between set point and cabin temp.
- auto will start to ramp down fan speeds as the cabin temp starts to approach set point.
- auto includes some A/C compressor operation. From what I've noticed in the winter, the compressor is running at low power, probably just enough to be effective at dehumidifying the cabin at a reasonable rate. The compressor does shut off eventually (you'll see the A/C button go from blue to gray), probably as a freeze protection measure.
- auto doesn't control the resistance heat. Meaning regardless of auto vs manual control of the HVAC system, the resistance heat kicks on depending on if your set point is higher than the cabin temp. It seems like there needs to be >1 degree difference for the resistance heat to kick in.
IN WARM WEATHER:
- auto will almost always run the A/C compressor, even if your set point is higher than the cabin temp. I believe this is to prevent the mildew smell that can build up in the vents. If you're in the habit of switching between A/C and fan only, you'll get the mildew smell.
- auto will ramp up or down fan speeds based on how close cabin temp is from set point.
- regardless of auto or manual control, in the evenings or mornings, if the outside air drops below your set point, the resistance heat kicks in. This IMO is super wasteful if you're trying to be energy-efficient. Since there is no fan-only button, the only option is to lower your set point, or turn off the HVAC completely.
IN COLD WEATHER:
- when the cabin is freezing and you set the temp to your desired temp, say, 72F, auto is smart enough not to blast the fan speed until the resistance heating elements are somewhat warm. Then it starts to increase fan speed.
- it is also smart about what percentage to vent from your feet vs face vs windshield, and the proportions will change depending on the difference between set point and cabin temp.
- auto will start to ramp down fan speeds as the cabin temp starts to approach set point.
- auto includes some A/C compressor operation. From what I've noticed in the winter, the compressor is running at low power, probably just enough to be effective at dehumidifying the cabin at a reasonable rate. The compressor does shut off eventually (you'll see the A/C button go from blue to gray), probably as a freeze protection measure.
- auto doesn't control the resistance heat. Meaning regardless of auto vs manual control of the HVAC system, the resistance heat kicks on depending on if your set point is higher than the cabin temp. It seems like there needs to be >1 degree difference for the resistance heat to kick in.
IN WARM WEATHER:
- auto will almost always run the A/C compressor, even if your set point is higher than the cabin temp. I believe this is to prevent the mildew smell that can build up in the vents. If you're in the habit of switching between A/C and fan only, you'll get the mildew smell.
- auto will ramp up or down fan speeds based on how close cabin temp is from set point.
- regardless of auto or manual control, in the evenings or mornings, if the outside air drops below your set point, the resistance heat kicks in. This IMO is super wasteful if you're trying to be energy-efficient. Since there is no fan-only button, the only option is to lower your set point, or turn off the HVAC completely.
Auto gets the cabin to the desired temperature... eventually.
It maintains the cabin at that temperature... somehow.
And most of the time it works.... reasonably well.
You'd think that the greater the temperature differential, the higher the fan speed. But it isn't always like that. My 2 previous cars they both had an OPTION of imposing manual fan control on top of the automatic temperature setting, which sometimes was necessary, because getting into a really hot cabin sometimes the fan was barely wheezing; or when the car is already chill, the AC decides to blast an arctic storm.
But for the most part auto climate control in most cars work well.
Though my favorite system was this Honda. All the controls were literally at my finger tips with hands in the standard driving position. The cabin was small so extremely easy to bring to temperature. And the 7 stage fan allowed you to set just the perfect speed.
You had to engage your HVAC options with a screwdriver?
What's that miracle ball in the middle of your console? Does it tell your fortune or something? <--------That's what the kids being born today are going to ask.
That's a nice write up you did. I wish in winter after it reached its temp instead of including some A/C it would not use A/C and turn off the heat if it cant go less then 1 .
Mine was an Alpine unit, way more tasteful than that Sony.
Less of an ape skin as well
The round ball (aftermarket "voodoo" shift knob) connected to the transmission with a direct linkage, and is still my reference to this day. People describing its action as 'rifle-bolt' weren't exaggerating at all! I've shot some rifles and they're equally satisfying!
Ivan Abundance
Member
Same as any other car. Turns the A/C compressor, temperature settings and fan speed to whatever the car (and its sensors) thinks is most appropriate.
Teslas aren't really magic. They just feel that way.
My question was.....
Whats the difference between having "auto" on and "auto" off. The car reaches the set temp either way.
Lastly. Teslas are magic. There is absolutely no way to explain the "Tesla smile" that's 18 months old other than magic.
So here is my two cents... Yes, the car may reach the same set temp either way BUT, you may use more energy if not on auto and fan speed of 1. There are a lot of variables obviously...where are you determining cabin temp? If you set to non-auto fan speed 1, no rear vent, and are measuring cabin temp in the back seat, then it may take longer to warm up the volume of air because of reduced air transfer vs general heat losses from all the glass.
All this is pretty hard to test though since you would ideally need to be able to control outside temperature as well as ensure you had the same starting ambient temp, and the same starting interior material temperature, since after running the test the first time you have heated up all the interior mass which could affect the results on the next test.
Indeed. You are exactly correct in saying that you use more energy using auto.
I proved that as I was sitting at a Tesla Destination Charger and had auto temp set to off. At that point I had 1 hour left to charge.
I turned on auto and my charge time to completion went up 15 min.
This morning I did the same thing and my charge time went up 25 min.
The only difference between yesterday and today that might be causing my charge time to increase is that I moved my temp up 1 degree.
Hmmmmm……..
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