Auto-AC Button on Steering Wheel

The Auto-AC button should have really been named "Climate Control." You set a temp for it to maintain, and it uses the AC or Heat to get it to that temp, and it will act on high humidity conditions too. I worried about that too and almost drove myself nuts when I first got the car, dinking around with the individual settings. Now I simply dial in a temp and let the car worry about it and it works great. Yes, the more conservative you are with its use, the more mpg you will get. In the summer I usually set Auto to 80 around town, it keeps me and my wife comfy even if its high 90s outside. In FL I dont think you have a real winter. Basically the heat takes heat from the engine, which costs gas to bring back up. Also, initially I think there are some heating elements that take voltage from the traction battery before the gas engine is warmed up.

 

Mine does this.

 

70 is a little low for some of the cars out there. it's a defect of sorts... or so it seems so far. never recalled or anything on here.

so.. there are a few on here. like me. who keep it around 80 in the mid summer to keep the battery from draining. others (seems to be the majority) say that they have no problem when it's about 100 out... set at 70 or less... so.. defect?

If you have someone that you can compare to, or many... you may be able to get a dealer to lean your direction. never being rude, of course.

 

Set the AC with the Climate window on the MFD. Then, whenever you want to enable or disable it, you have the option of pressing the Auto/AC button on the wheel. As your set temperature approaches the outside temperature, the fan slows down. If the set temperature is higher than the outside temperature, the produced airflow becomes warmer.

 

btw.. there is a sensor on the dash. if light is pointing in through the windshield, the fans are turned up.

 

It does, as long as there is a set temperature. It doesn't if you set "MAX COLD" or "MAX HOT".

Also, after selecting AUTO, you can override the fan speed or vent flows on the touchscreen, and you go into a "partial auto" mode - other functions remain on automatic, except for what you manually selected. Reselecting AUTO puts everything back to automatic. So if you touch a fan speed control after selecting AUTO, it won't change the fan speed.

 

i live in the same area as op, set mine at 76 and it does the rest all from the buttons on the steering wheel

 

To answer your second question, the A/C compressor on the Prius is even smarter than your one at home. Rather than using a simple on/off thermostat (bang-bang control), the Prius uses a proportional system. It runs the compressor faster if it needs more cooling, slower if it needs less.

As for temperature setpoint, don't worry too much about what the numbers say. Depending on the sun and how I am dressed, and whether I need heat or cooling, some days I am fine with 78, other days I set it on 68. Use the temperature buttons on the steering wheel as comfort and fan adjusters: if you need it cooler drop the temperature a few clicks. It's that simple.

Tom

 

the more colder you set the auto a/c on the more the car will run on battery
the more warmer you set the auto a/c on the more the car will run on the ICE

sitting on my lunch break with the car in READY for 30 minutes and auto AC set
to 72 causes the ICE to only be on for 5% of the time

this is valid for toyota prius cars with the electrical a/c system thingy

 

must be south florida... face it, at 70º, the fan may never adjust. here on the opposite end, it set mine at 68-75, (my comfort level varies, usually based on the amount of radiant heat, or sunshine...)

the fan speed starts on high, but most of the time, it starts to kick down after less than 5 mins...

 

In my experience, if it's hot outside and you have the temp any lower than 72, it stays in recirculate mode and the fan blows fairly fast all the time.

I use 72 in the summer and 70 in the winter and it seems best for me.

 

has nothing to do with so florida, op is not understanding posts and thinks like i did with my rav4, turn a/c on and temp control to blue area. he only mentions 70 and 80 degree settings, i keep mine at 76-77 always and it does the rest, i put it to 70 after golf the other day and it stayed on too long as op stated, set it up a few degrees and all was well adjusting fan speed and cold air all by itself..amazing

 

the point i am trying to make is that the higher the temperature you have auto a/c set to the more likely your prius is going to burn more gasoline....

if you care about fuel enonomy and want to keep the engine from kicking on you would set your a/c down from the upper 70s to the lower 70s, like 72

based from my observatoins, the prius does not warm up the cabin from warm air outside, it warms it up like a regular car would, via its internal combustian engine

 

I am pretty sure I read somewhere in the manual that to get most efficiency out of using the A/C is to keep it at two degrees below the outside temperature. Now no matter how unrealistic this would be, especially if it is like 95 out, I think it helps to keep the windows open the first 5 mins of driving and then putting the A/C on at around 75. It is about 80-90 degrees during the day and it is plenty cool enough without much change in gas mileage.

 

This is misleading. The Prius uses heat from the ICE to warm the cabin when heat is required, and uses HV electricity to cool the cabin when A/C is required. Both of these conditions use energy, which ultimately came from burning gasoline. Best mileage will come from not needing to heat or cool. If you raise the temperature setpoint when cooling, the Prius will allow the cabin to warm by reducing the amount of cooling. The converse is true when heating in the winter.

If you rapidly raise or lower the setpoint, it is possible the Prius may use heat or cooling to get there, rather than waiting for ambient conditions to do the job. This is because the Prius uses a proportional control system, either PI or PID, to control heating and cooling. Outside air temperature, humidity, cabin temperature, setpoint, and solar intensity are all used as control inputs and influence the decision of when and how much heating and cooling is needed.

There are a couple of special cases that may be confusing you. Cabin air is used to cool the traction battery. If you allow the cabin to get too warm, it will interfere with operation of the traction battery. The other special case is max heat with a cold engine. There are two electric heating elements that come into play in this special case, thereby using HV electricity for heat.

Other than that, your cabin temperature setting has nothing to do with fuel economy.

Tom

 

that would be wrong.

let me restate that i have set AC as low as 68º and the fan speed still kicks down after a time...so it is either his AC is not functioning properly, or it has to do with his environment. i doubt the former is the case here.

you say its because he sets it to 70º... well, maybe not the recommended setting, but in itself, the setting does not make the AC work improperly.

now i would still recommend setting the temp higher since it would give instant feedback that the thermostat does work.

 

set the temperature to whatever you like and when you feel comfy, turn the temp up until the fans slow down a little. it is possible to actually be cold in the prius when it's hot outside... on a long car trip, i set auto A/C at 73 and it started getting a little chilly since it was only about 80 outside that night so i raised the temp up to about 75 and it was very comfy.

 

just set the thermostat for where you would like the temp to be.

On auto-ac it will get it there as best it can with fast fan then slower fan when it gets closer. In FL just now the outside temps are near 100* for me so I set at 80* and let the car figure the rest out. 80* is surprisingly cool when it's triple digits outside!