Auto A/C

Last winter I tried to be in control of the system, AC, fan, outlets, etc. This year I decided to just leave it in Auto AC and let the system run it's self. The only advantage I can find to being in control of the system is that you learn how everything works. I have noticed no difference in mileage.

 

I leave it on, just set it and forget it. Unless you are really obsessed with MPG the 1-2 MPG hit is insignificant. TonyPSchaefer put it well when he said, "You can think of the A/C as a variable system. Basically, if allowed to do it's thing without human interference, it will work extremely efficiently."

 

Yep, just set it and forget it.

We are however extremely dissapointed with the quality of the Prius' auto climate system. I've had a lot of cars with auto climate control, and the Prius has the hardest time keeping the interior cool or warm. You're always freezing in the winter and sweltering AND listining to the loud fan in the summer.

 

<div class='quotetop'>QUOTE(Renocat @ Nov 5 2006, 10:57 AM) [snapback]344083[/snapback]</div>

One of the posters here with the monitoring software (CANVIEW I think?) reports that the engine gets up to operating temperature quicker if you don't turn the heat on for the first few minutes. I just leave it set though, for the most part, and get in and drive.

 

I mostly set it to a lowish temperature and forget it. It works pretty well. The one caveat is that I sometimes turn the AC off when I stop at a light and the engine it cold in order to let the engine shut off.

 

Does the Prius use hot coolant for cabin heat like a traditional car, electric heat, or both? I have read that the Prius uses electric heaters, which makes certain sense and would match the electric A/C...but I have to believe that electric heat of any power would rapidly drain the battery. Is ICE heat also used when available? If ICE is used, wouldn't that also lower mileage?

 

The Prius uses both electric coils and hot coolant for heating. My understanding is that the primary function for the electric coils is to delay the ICE from restarting if the car is stopped and the coolant has cooled to the point that it really can't keep the cabin warm. I also believe that the electric coils might also be used to help warm up the cabin more quickly when you first start driving the car.

Why bother with conventional hot coolant heating when you have all that electricity available? It would take considerable power to electrically heat the car, and besides, once the engine is up to operating temperature, there is plenty of excess heat available for use.

 

<div class='quotetop'>QUOTE(SW03ES @ Nov 5 2006, 11:46 AM) [snapback]344098[/snapback]</div>

Not in my experience. What outside temperatures are you talking about? Do you adjust the setting of the interior temperature when necessary?

 

<div class='quotetop'>QUOTE(SW03ES @ Nov 5 2006, 08:46 AM) [snapback]344098[/snapback]</div>

You either don't use AUTO/AC or have a problem with the climate control.

 

FWIW, i don't use the A/C or heat at all... just leave it off all the time. The summer is great with the windows down, and in the winter i'm already all bundled up anyways - no sense in turning the heat on so i get hot and have to start stripping in the car...

 

<div class='quotetop'>QUOTE(eagle33199 @ Nov 6 2006, 06:48 AM) [snapback]344461[/snapback]</div>

Don’t remember who to attribute this to but they say it much better than I could.

“I cannot stress this enough, use your A/C or loose it. The health of an A/C system is based upon it being used. Compressed refrigerant, as it goes through the system, carries with it refrigeration oil, which is mostly used to lubricate the compressor, but also keeps the o-rings and seals fresh and soft. If you intentionally choose to not use the A/C you are choosing to let the system dry out and that will require future expense to bring it alive again. The Prius battery also requires a "room temperature" environment for most efficient operation. If the interior of your cabin is hot after sitting out in the sun, the Prius uses the climate control system to bring the cabin temp down to a level which helps the battery operate efficiently. The battery does not run efficiently above 100 degrees and doesn't do that well when it is freezing out, so a pleasant cabin temp is also pleasant for the battery.

So, what I'm saying is that you should never defeat the A/C system as it does more than just keep you comfortable.â€

 

yes, on longer trips i'll use it - but those generally only come along once a week or so... most of the trips are very short - what benefit is the battery going to see from having the heat on for a 6 mile commute?

There's a definite trade off between comfort and mileage... using the heater in the winter will cause a longer warm up time for the engine - not a problem if you're going to be in the car for 30min+. but when you're in the car for a 12 minute commute, you get where you're going practically before the warm up is over, and the heater won't even have done all that much yet (especially considering how much cabin heat it actually takes to warm up a completely cold battery...).

 

I leave the system in Auto mode and just adjust temp up/down as needed to adjust how strongly the fan blows, and out of which vents. In the winter, I will switch to defrost mode as necessary to clear the front windshield. I find this much easier than having to hit the climate button on the MFD and select whether A/C is on or off, what vents the air is coming out of, what my temperature set point is, and how fast the air blows, etc. Ironically enough, our Sienna also has auto climate control as well, but we hardly ever use it. Instead we manually pick fan settings, etc. Why? Probably because the controls are right there and I don't necessarily have to look at a screen to change the settings. I can just feel my way around without taking my eyes off of the road. Go figure...

I don't have the problem of freezing in the winter or sweltering in the summer that another poster complained about. Yes, the fan can get loud in the summer, usually when you've just gotten in the car on a hot summer day and it is set to some low set point, like 70. I find that if I a) roll the windows down to exhaust the hot air in the cabin for a minute, and B) pick a slighter higher temp set point, the fan will settle down to a much quieter setting, and the cabin will be very comfortable very quickly.

While the idea of the Auto setting is so that you can set a preffered temp to have and the system will do all that it can do to maintain that, it doesn't necessarily mean that that specific set point is appropiate year-round, or when you first get in the car versus when you get to your destination. Auto to me means that it manages to fan settings, A/C compressor on/off, and vent settings for me so that I can concentrate on picking a temp set point that will make me comfortable.

 

Being obsessive about mileage (should have never got that 1st 600 mile range tank / 60+mpg) I tend to keep AC & Heat to a minimum so as to eek out that extrra mpg.