Turning on rear vents for AC

[Needsdecaf]

Nothing is faulty if no one is in the back the vent does not turn on so I buckle a belt and it turns on the vent when I drive with my dog in the backseat .

Not sure why everyone thinks something is wrong and is arguing...

It is just any easy way for me to turn the rear vents on, dog jumps in I buckle a belt.

Thought I would share that’s all.

We're arguing because you don't need to do what you're doing. I turn my rear seat vents on and off all the time with no one back there, and no seatbelts buckled. Just use the button on the screen to turn it on or off. It's very easy to verify the effect, just reach your hand around behind you and feel the vents. As soon as I touch the button, those vents turn on or off.

Thank you!
The weight sensor does not detect my toddler in the back seat so I ALWAYS have to manually turn on the rear vents. This is a good work-around (for those of us that use AUTO climate).

In Auto, just tap the button on the screen to turn airflow on in the back. Do not need to worry about weight sensors or seatbelts at all. That's why the control is there.

 

[justsomeguy]

When I picked up my old car after having service done, or when I get in a rental, the AC is always set as cold as it will go with the fan on high, like that's going to cool it down faster. People have a misunderstanding that they are affecting the temperature of the air being blown.

Yup. Just like the people who set their oven to the max setting to preheat faster.

 

[darth_vad3r]

When I picked up my old car after having service done, or when I get in a rental, the AC is always set as cold as it will go with the fan on high, like that's going to cool it down faster. People have a misunderstanding that they are affecting the temperature of the air being blown.

Yup. Just like the people who set their oven to the max setting to preheat faster.

Well, for a BBQ grill this actually can be true. It could also be true for a gas oven or electric oven, depending on the design ... it is designed to hit a set point and stay there, with little to no overshoot. If you are okay with overshoot, and just want to get to “at least X degrees” as quick as possible (because you are freezing your buns off) then you want the heating elements on max. Who is to say the Tesla HVAC system doesn’t control the temperature of the heating elements, especially for heat where it’s not ‘free’ waste heat, why waste electricity sending more current than necessary through the heating elements than necessary? But if you put it on HI, the heaters will get max current. The air temperature flowing through the vents will actually get warmer.

The HVAC system on the Model 3 may also do something similar for cooling. It’s not the exact same design as in a typical ICE vehicle.

If you want your water to get to a simmer faster, should you set it to the final simmer setting, say 5/10, or should you set it to 10/10 and then back it off once it reaches the simmer?

You are assuming a constant heat or cooling output, but that’s not necessarily how the Tesla HVAC system works.

Comparing to a home thermostat, where the thermal mass in the house is massive, and heat changes are relatively slow compared to within a car where you can change 20 degrees within minutes, is not a good comparison.

In a home, leave the thermostat where you want it. In an EV, if it’s freezing, and if you want comfort as soon as possible, turn it beyond where you want it, then dial it down once it reaches a comfortable temp.

The same can be said for ICE ... setting the “temp” is likely mixing different ratios of fresh vs hot waste-heat carrying air, so if you want to heat the cabin as quickly as possible you set it to max temp.

Just like if you have a bathtub half full of luke warm water and you want to heat it up, you max the water being added to scalding hot, not to ‘warm’ and wait longer to warm up the entire tub.

 

[justsomeguy]

Well, for a BBQ grill this actually can be true. It could also be true for a gas oven or electric oven, depending on the design ... it is designed to hit a set point and stay there, with little to no overshoot. If you are okay with overshoot, and just want to get to “at least X degrees” as quick as possible (because you are freezing your buns off) then you want the heating elements on max.

This is exactly how automatic HVAC will do it. Especially in an ICE vehicle where AC compressor speed and heat can not be controlled, only the air mix and duty cycle

Who is to say the Tesla HVAC system doesn’t control the temperature of the heating elements, especially for heat where it’s not ‘free’ waste heat, why waste electricity sending more current than necessary through the heating elements than necessary? But if you put it on HI, the heaters will get max current. The air temperature flowing through the vents will actually get warmer.

You're speculating, but I still think it's wrong. If you turn on the heater when the car is very cold, it will max the heating element (you can observe this very easily by seeing your power draw either plugged in to the wall or in your efficiency numbers while driving) and probably taper it down when you're close to the set temperature. At that point, even the people who just hit MAX will already be comfortable. There really is no reason to do this.

The HVAC system on the Model 3 may also do something similar for cooling. It’s not the exact same design as in a typical ICE vehicle.

Again, the HVAC system on the Model 3 will crank the AC to get you down very close to your set temperature before it tapers. You're talking about a difference that is insignificant, as your discomfort and desire to "crank" the settings is typically only experienced when the car is at ambient (or baking in the sun).

If you want your water to get to a simmer faster, should you set it to the final simmer setting, say 5/10, or should you set it to 10/10 and then back it off once it reaches the simmer?

This is not a good comparison. You're setting a power level and not a temperature. If you were to tell a theoretical 'smart' range to "boil, then simmer" it would do exactly as a human would. Crank the heat, boil, then lower to simmer.

You are assuming a constant heat or cooling output, but that’s not necessarily how the Tesla HVAC system works.

Comparing to a home thermostat, where the thermal mass in the house is massive, and heat changes are relatively slow compared to within a car where you can change 20 degrees within minutes, is not a good comparison.

And I can guarantee you people who design automatic HVAC systems in cars take this in to account.

In a home, leave the thermostat where you want it. In an EV, if it’s freezing, and if you want comfort as soon as possible, turn it beyond where you want it, then dial it down once it reaches a comfortable temp.

Or set it to your desired temperature and watch your car do almost exactly the same thing.

The same can be said for ICE ... setting the “temp” is likely mixing different ratios of fresh vs hot waste-heat carrying air, so if you want to heat the cabin as quickly as possible you set it to max temp.

Setting your heat to MAX just blows more air over the heater core when it's not warmed up. The available heat is a function of how warm the engine is. You're probably just making yourself colder by increasing the amount of cold air flowing over your face.

Just like if you have a bathtub half full of luke warm water and you want to heat it up, you max the water being added to scalding hot, not to ‘warm’ and wait longer to warm up the entire tub.

Again, not programming a temperature. Your automatic HVAC isn't going to mix cold and hot air when you're very far off your set temp. It will intelligently condition the air by getting you to your set temp as fast as possible.

 

[darth_vad3r]

If you turn on the heater when the car is very cold, it will max the heating element (you can observe this very easily by seeing your power draw either plugged in to the wall or in your efficiency numbers while driving) and probably taper it down when you're close to the set temperature..

You say I’m speculating and probably wrong, then you actually agree with me and say it probably tapers.

It tapers to not overshoot. If you want to get from 10C to 20C the absolute fastest, it would be faster to set it to HI, then to set it to 20C, because of the taper that you just agreed with. That’s my point.

 

[darth_vad3r]

Or set it to your desired temperature and watch your car do almost exactly the same thing.

Again, agreeing with me. ALMOST the same thing. So if you want the absolute fastest, you do it the way people are making fun of and say has no effect. It has an effect. That’s my point.

Again, not programming a temperature. Your automatic HVAC isn't going to mix cold and hot air when you're very far off your set temp. It will intelligently condition the air by getting you to your set temp as fast as possible.

No, because it tapers to not overshoot once it get close, it doesn’t do it as fast as possible. To reach it as fast as possible (if you don’t care about overshoot) it is best to set to LO or HI.

It (auto) does it fast, initially it would be max or close to it, but it TAPERS, thus making it not reach the set point “as fast as possible”. By definition of what taper means.

If we are in a race to a finish line, I’ll go as fast as I can.

If we are in a race to a finish line but I have to stop at the finish line, I’m going to slow down before I get to the finish.

The first person will get to the finish line faster.

You can shift the goal posts all you like and say “it’s almost the same” or not that much faster.... but it IS faster, and thus making fun of it and saying it has no effect is not justified IMO.

 

[justsomeguy]

If that's your argument there's really no point continuing this discussion. Why do people set LO or HI? Because their car is either uncomfortably hot or cold, respectively. Setting auto temp will get you comfortable equally fast as cranking it, and saves you from having to micromanage your HVAC settings.

In the oven case I guarantee you will save no time at all.

 

[darth_vad3r]

If that's your argument there's really no point continuing this discussion. Why do people set LO or HI? Because their car is either uncomfortably hot or cold, respectively. Setting auto temp will get you comfortable equally fast as cranking it, and saves you from having to micromanage your HVAC settings.

In the oven case I guarantee you will save no time at all.

It’s not EQUALLY as fast. Stop saying that, it’s incorrect. You’ve already stipulated this in prior posts.

“Comfortable” will equate to some temperature warmer or cooler than it currently is. “Auto” will taper at some point, thus delaying getting to that ‘comfortable’ temp, even if ‘comfortable’ is closer than your set temp.

It’s not really micromanaging to blast it to HI or LO for a couple minutes then set it back to a nice comfy temp.

The defrost does this, I have to do that when the windows fog up anyways.

 

[Kimmi]

The dead rise!
Will the car cool quicker if the rear vents are on with no one in the seats?