AC setting to save gas?

[mike_m]

I have always got in all of my cars and set temp to "max" cold and usually "low" on the fan. It wasn't til I was reading my manual that the "auto" setting might be the way to go. Does the auto feature work just like a home AC? For example; If I set it on 73, will it come on and off to maintain that temp? The reason I ask is, everytime I have used the auto button in cars, it always comes on full blast. Does it do that just to cool off then adjusts itself? Last question: If the fan is too strong on auto, and I turn it to low, does it automatically turn to manual? There has to be something there to save gas. It's way too hot here in FL. not to use AC.

[AnOldHouse]

<div class='quotetop'>QUOTE(mike_m @ Jun 6 2006, 04:29 PM) [snapback]266852[/snapback]</div>

I have always got in all of my cars and set temp to "max" cold and usually "low" on the fan. It wasn't til I was reading my manual that the "auto" setting might be the way to go. Does the auto feature work just like a home AC?[/b]

Not exactly.

<div class='quotetop'>QUOTE(mike_m @ Jun 6 2006, 04:29 PM) [snapback]266852[/snapback]</div>

For example; If I set it on 73, will it come on and off to maintain that temp?[/b]

The fan will not go "on and off", but the compressor cycle will once the cabin is to set temperature. It will start with as much fan and also recirculated air as needed. It it's hot out, this means full blast fan and recirc air. As cabin temperature comes near set target, recirc will go off and the fan setting will notch down incrementally through the available speeds automatically. Once at temp, the fan will run at a very low speed for temp maintenance.

<div class='quotetop'>QUOTE(mike_m @ Jun 6 2006, 04:29 PM) [snapback]266852[/snapback]</div>

The reason I ask is, everytime I have used the auto button in cars, it always comes on full blast.[/b]

As will the Prius.

<div class='quotetop'>QUOTE(mike_m @ Jun 6 2006, 04:29 PM) [snapback]266852[/snapback]</div>

Does it do that just to cool off then adjusts itself?[/b]

Yup!

<div class='quotetop'>QUOTE(mike_m @ Jun 6 2006, 04:29 PM) [snapback]266852[/snapback]</div>

Last question: If the fan is too strong on auto, and I turn it to low, does it automatically turn to manual?[/b]

Yes. Any screen adjustment, other than set temp, to the climate control will take it out of automatic.

<div class='quotetop'>QUOTE(mike_m @ Jun 6 2006, 04:29 PM) [snapback]266852[/snapback]</div>

There has to be something there to save gas. It's way too hot here in FL. not to use AC.[/b]

AC's a hit, but I don't think it's enormous and remember that winters up north here kill our MPG's too. It's only fair! Use the Auto AC. If you're going highway speeds anyway, AC is a wash because of the air drag that would be caused by opening the windows. When it's nice out and you're just driving around town, turn the AC off completely and roll down the windows and enjoy. If it's cooler out than it is in the car, drive with the windows down for a few minutes to blow out the hot air quickly. Consider using window shades if you park in the sun. Also AC is more efficient on longer drives because you only have to cool down the cabin once and then just maintain that.

[mike_m]

<div class='quotetop'>QUOTE(AnOldHouse @ Jun 6 2006, 05:29 PM) [snapback]266892[/snapback]</div>

Not exactly.

The fan will not go "on and off", but the compressor cycle will once the cabin is to set temperature. It will start with as much fan and also recirculated air as needed. It it's hot out, this means full blast fan and recirc air. As cabin temperature comes near set target, recirc will go off and the fan setting will notch down incrementally through the available speeds automatically. Once at temp, the fan will run at a very low speed for temp maintenance.

As will the Prius.

Yup!

Yes. Any screen adjustment, other than set temp, to the climate control will take it out of automatic.

AC's a hit, but I don't think it's enormous and remember that winters up north here kill our MPG's too. It's only fair! Use the Auto AC. If you're going highway speeds anyway, AC is a wash because of the air drag that would be caused by opening the windows. When it's nice out and you're just driving around town, turn the AC off completely and roll down the windows and enjoy. If it's cooler out than it is in the car, drive with the windows down for a few minutes to blow out the hot air quickly. Consider using window shades if you park in the sun. Also AC is more efficient on longer drives because you only have to cool down the cabin once and then just maintain that.
[/b]

Thanks David. I went and sat in the car for a while and saw that the fan does turn itself down as desired temp. is achieved. I noticed when the fan was on medium and I adjusted the temp up, that turned the fan down to low. All these years, I never knew that, DUHHHHHHHHHHHHHHH.

BTW, I filled up with my second tank today, and averaged 45 MPG for 80 miles. I am happy about that. I was sure that I would never see over 40 consistently with the big tires and wheels. I slowed down, anticipating stops, and the mileage shot right up. This whole speed limit thing is kinda neat!

[Tideland Prius]

I think David gave a pretty good response. if you wanted to try, set the climate control at the highest possible temperature you can withstand while staying cool. That way, the A/C isn't cooling the interior unnecessarily. Today, I had the A/C at 22°C. Then it got cold and I kept bumping it up til it was at 24°C and I was still comfortable.

[MarieH]

In the Prius, I'm comfortable with the temp set around 75 or so...in my old car it had to be on 70 to be cool enough. Wonder if the Prius a/c is just more efficient. On cool nights, I just turn the fan on to keep some air moving, and turn the a/c off. That's probably not going to be something you can do anytime soon in Florida!

[TonyPSchaefer]

I don't like the full-blast A/C blowing. It's loud and windy. So when I turn on the A/C I turn it all the way up to 85ºF since the interior's warmer than that. Then after a while, I slowly cycle it down if I start feeling warm.

[powrfuel]

<div class='quotetop'>QUOTE(TonyPSchaefer @ Jun 7 2006, 05:09 AM) [snapback]267161[/snapback]</div>

I don't like the full-blast A/C blowing. It's loud and windy. So when I turn on the A/C I turn it all the way up to 85ºF since the interior's warmer than that. Then after a while, I slowly cycle it down if I start feeling warm.
[/b]

i set mine at 68...like it cold

[NuShrike]

78-80F works just fine for me in Los Angeles. 49-50MPG so far @ 102Km/h.

[CrazyRussian]

Yes. Any screen adjustment, other than set temp, to the climate control will take it out of automatic.
[/b]

I dont think this is correct. I remember reading somewhere in the manual, I think, that whatever changes made to AC settings will set to manual only that particular setting, the rest of AC functions will still be on AUTO. From my personal experience, if I change fan speed, while the AC is on AUTO, the rest of the AC functions are still auto: recirclulating is auto, air distribution (which vents are used) is auto, the air also changes in temperature which makes me to believe that the car using the compressor to adjust the temperature in order to keep it at the set level while the fan is on manual.

Also, as I mentioned in my other post "AC impact on MPG", using AUTO when difference between "comfort" temperature and outside air is high, kills MPG by at least 10. Again, all of this is from my personal experience and I dont have anything, except my personal observations and testing, to back it up. Temperature here, AZ, stays above 100 for a few weeks already, and obove 110 for almost a week. If I use AUTO right from the start of my commute home from work, at about 3:30 PM, I see my MPG drops and AC is on full blast for at least 25 minutes. If I manualy set the fan speed to one less from the middle, while the rest is on AUTO, and then switch to full AUTO when temp inside is cooled down, about 15 minutes, MPG decreases only by about 2-4 MPG. I did quite a few experiments with different settings while taking the exact same commute and this approach seems to be the best compromise between MPG and a comfort zone, at least for me.

[AnOldHouse]

<div class='quotetop'>QUOTE(CrazyRussian @ Jun 7 2006, 11:32 AM) [snapback]267240[/snapback]</div>

I dont think this is correct. I remember reading somewhere in the manual, I think, that whatever changes made to AC settings will set to manual only that particular setting, the rest of AC functions will still be on AUTO. From my personal experience, if I change fan speed, while the AC is on AUTO, the rest of the AC functions are still auto: recirclulating is auto, air distribution (which vents are used) is auto, the air also changes in temperature which makes me to believe that the car using the compressor to adjust the temperature in order to keep it at the set level while the fan is on manual.[/b]

In addition to the temp adjustment not taking it out of A/C AUTO mode, you can toggle the recirc air on and off without taking it out of AUTO.

But changing the fan speed or the the vent directions or turn off the A/C button (the compressor) all do take it out of AUTO. I'm going by the A/C AUTO indicator light on the dash board.