HVAC question. What does "AUTO" do?

[Garlan Garner]

Ok....

So I turn on the heat in my car to 69 degrees F.

The outside temp is currently 32 degrees F.

The fan speed is 1.


I can dial up the Temp to 72 and sure enough it gets up to 72.

NOW I turn on the "AUTO" feature and the fan cranks up ( still set to 72 ).

What does "AUTO" do? The temp of the car gets to 72 degrees either way.

 

[DopeGhoti]

The "Auto" setting will crank the fan speed up higher at greater differentials between the set and observed temperatures.

 

[Garlan Garner]

The "Auto" setting will crank the fan speed up higher at greater differentials between the set and observed temperatures.

hmmmm…..interesting.

If that's true.....then its kinda useless to me.

I know Auto uses quite a bit of charging energy. I was chagrining at a Tesla Destination charger this morning and I had an hour left to charge. I'm sitting in the car playing around with the settings and I turned on the "auto" setting and my charge time went up to 1 hour and 20 min. Whoahhhh….

 

[eladts]

hmmmm…..interesting.

If that's true.....then its kinda useless to me.

Why? Just use it as you use the AC at home. Set the temperature you like and forget about it. From my experience the "Auto" setting allows you to do just that.

 

[DopeGhoti]

Auto will also turn the AC compressor on and off as needed. When it's on, it does draw power. Currently there is no way to use "Auto with no A/C compressor", but then most cars with "auto" settings have the same perceived deficiency.

 

[Garlan Garner]

Auto will also turn the AC compressor on and off as needed. When it's on, it does draw power. Currently there is no way to use "Auto with no A/C compressor", but then most cars with "auto" settings have the same perceived deficiency.

Hey that leads me to another question.


Why is the AC compressor on during heating ?

Its 32 degrees outside and I have the heat on. However the AC shows that its on. hmmmmm.

 

[Garlan Garner]

Why? Just use it as you use the AC at home. Set the temperature you like and forget about it. From my experience the "Auto" setting allows you to do just that.

You can set the temperature either way.

My car heats up without "auto" on and with "auto" on.

My house doesn't have 2 options.

 

[Darmie]

Hey that leads me to another question.


Why is the AC compressor on during heating ?

Its 32 degrees outside and I have the heat on. However the AC shows that its on. hmmmmm.

Helps with defogging windshield. There are times when using Manual that I will cycle the A/C to keep from fogging windshield and side windows.

 

[XHabjab]

You can set the temperature either way.

My car heats up without "auto" on and with "auto" on.

My house doesn't have 2 options.

Every home thermostat I've seen has a switch that has settings of "On", "Off", "Auto"...

 

[Msjulie]

Auto shouldn't engage heat unless it has to; frequently I turn on the climate control and only AC runs because though it is colder outside, ambient air temp, the solar load in the car has raised the temp higher than what I requested. My understanding of auto is it will maintain the temp you set using heat and/or cooling as needed and not otherwise.

I wish setting a single low speed fan only required less taps but I'm nitpicking

 

[Garlan Garner]

Auto shouldn't engage heat unless it has to; frequently I turn on the climate control and only AC runs because though it is colder outside, ambient air temp, the solar load in the car has raised the temp higher than what I requested. My understanding of auto is it will maintain the temp you set using heat and/or cooling as needed and not otherwise.

I wish setting a single low speed fan only required less taps but I'm nitpicking

What happens when you set 70 degrees without "auto" selected?

Doesn't your car hover at 70 degrees?

 

[Msjulie]

What happens when you select 70 degrees without "auto" selected?

I've not done that but will give it a shot and report back later

Edit: Manual says

"By default, climate control is set to the Auto setting, which maintains optimum comfort in all but the most severe weather conditions. When you adjust the cabin temperature in the Auto setting, the system automatically adjusts the heating, air conditioning, air distribution, and fan speed to maintain the cabin at your selected temperature"

 

[ewoodrick]

Auto keeps the car near the set temperature. It requires no constant twiddling and should be pretty battery efficient. It only turns things on ehwh needed.

 

[run-the-joules]

Helps with defogging windshield. There are times when using Manual that I will cycle the A/C to keep from fogging windshield and side windows.

The amount of times I see people running around in winter with fogged glass because they don't understand the most basic principles of air CONDITIONING (not air COOLING)… sigh.

Uber drivers in NYC are the absolute worst about this, as far as I can tell.


I use Auto mode because it works reasonably well, personally.

I do wish there was a way to make sure it always keeps the fan blowing because sometimes when it's set to a temp similar to what's outside, it doesn't circulate air and it becomes awful and stagnant like I'm in a car with one of those savages who turns the HVAC completely off. When that happens I just turn the temp down a few degrees.

 

[ewoodrick]

hmmmm…..interesting.

If that's true.....then its kinda useless to me.

I know Auto uses quite a bit of charging energy. I was chagrining at a Tesla Destination charger this morning and I had an hour left to charge. I'm sitting in the car playing around with the settings and I turned on the "auto" setting and my charge time went up to 1 hour and 20 min. Whoahhhh….

Give it a few minutes

 

[Twiglett]

In summer the fan never seems to blow fast enough to keep cool. I usually have to turn the fan up to keep my head cool

 

[DopeGhoti]

Why is the AC compressor on during heating ?

Because air conditioning isn't just for cooling. You can condition the air to be hot too.

 

[Rothgarr]

I don't think I ever NOT use "auto". Just dial in the temp and the fan speed up or slows down as needed. For me I only need two settings: "Auto" and "Off"

 

[Eno Deb]

In summer the fan never seems to blow fast enough to keep cool. I usually have to turn the fan up to keep my head cool

Conversely, at low temperatures like now it often blows to strong for my (and my better half's) taste. I wish it was possible to select the windshield/front/footwell vents in Auto mode, and perhaps to turn off the left and right front vents selectively.

 

[Big Dog]

protip: the temp sensor is in in the rearview mirror apparatus. Why that is important is if you have the vents blowing up the windshield, it will cool the temp sensor but not necessarily your face. (I sat in the sun and measured with two thermometers. The air surrounding the temp sensor measured 72 degrees as the vents were blowing at Auto speed 3, but the air around my center console was more like 77 degrees.)

So, for those Auto folks (like me), check your vent settings and move them more to the outside windshield and not straight up the middle. What this will do is maintain the middle part of the car -- and your body -- at closer your set point, and not just the temp sensor high up on the inside of the roof. By redirecting the air flow away from the temp sensor of the car, you get more fan speed on Auto.

And yes, Garlan, the compressor dehumidifies (all that hot, steamy air coming out of the passenger's mouths and noses).