Air Conditioner

When in auto mode it selects recirculation. Will the car then change to fresh after your desired temp has been achieved?

 

Yes, but it may take a good while.

 

Also will the car turn the ac off in auto mode if the cabin is getting too cool. I had it set at 75 today and noticed the smell like the air conditioner had kicked off, or when you turn it off. I was driving through the mountains and the outside air changed to 68. I think the car may have been turning the a/c on and off.

 

I only use ECO mode and prefer to manually adjust the a/c rather than auto control, believing I'll get better MPGs. Lately, I've started hyper-miling with my a/c controls. Once cabin temp is comfortable, I'll turn off the a/c, and leave fan on low. I do this especially in both city and highway speeds. I can't tell yet whether or not this makes any significant improvement on MPGs, but I'm still researching. On paper, a/c hyper-miling sounds practical, but in reality I'm concluding it won't have any significant impact.

 

Actually, this doesn't seem to be quite true. I leave my 2010 in ECO mode all the time and while it definitely favors recirculation it doesn't use it exclusively. I've found in the mornings... typically when the outside temp is close to the cabin temp it will still switch out of recirculation for 5 to 10 minute periods.

 

I think it depends a lot on the outside temp and how much the AC needs to work. When I first got my prius in January (remember I'm in FL, so it can be in the 70's or even 80's here in January) I noticed that I got similar MPG numbers on my commute to work and my commute home from work. Now that it's summer and it's often in the high 90's when I'm driving home from work I typically get 5-10MPG on the trip home than on the trip to work. On the rare days when it's cooler out when I'm driving home I get that 5-10 MPG back. I haven't tried leaving the AC off on a warm day just to see if my economy improves, but I'm reasonably certain that it would.

Also, I have a scangauge and one of the XGauges I've configured shows how many amps the AC compressor is drawing... when it's in the 90's out and the car has been sitting in the hot sun all day the compressor will draw nearly 10 amps for 10 or 15 minutes until the car is cooled down... once the car is cool that drops back to only 3 or 4 amps to keep it cool. When I drive into work in the morning and it's in the 70's out and the car is cool to start with the AC compressor only draws 1 or 2 amps, and often even cycles on and off, drawing 0 amps at times.

So, I think the short version is... the Prius does a very good job of managing the AC power usage on it's own and I'm not sure you can save a whole lot by trying to turn the AC on and off on your own... unless you're willing to just turn it off and leave it off and deal with a hot car.