A/C AUTO -- set it and forget it?

I leave mine in Auto A/C all year and adjust the comfort level with the temperature control. Keep in mind that the AC compressor is electric and will only run when needed for cooling and humidity control. It doesn't use that much gas.

 

+1 on that. Keep in mind that not only is the compressor electrically driven, but it is variable speed. It only runs as much as needed.

Tom

 

The only thing that I'd add to the "set it and forget it" philosophy is that I find on very hot days I sometimes have to force the system to re-circulate air instead of trying to bring air in from outside. The car never will cool down if it tries to bring 95+ degree air in from outside and cool it to my set point. However, if I just hit the re-circulate button, the car cools down reasonably quickly.

I'm guessing that this may also be true in very cold temperatures with the heater on instead of the AC compressor.

 

Yes, but I also force re-circ because I hate breathing Diesel exhaust.

 

I like a lot of fresh air, so most of the year I have the system set on 'max cold' to force the vent setting. "Too hot" for me kicks in at about 40C, and "too cold" means putting on another layer. Other than the all-too-rare vacation, most of my driving is Dad's taxi service. I'll toggle the defrost as needed, but usually I'm not going far enough for the heating or cooling to have much effect. Yes, I know short trips aren't good for the mileage, but neither is driving out of my way just to bring the average consumption down.

 

There's that too....funny, but that's usually the thing that reminds me that the car has flipped over to "vent", when it's 95 out and I can smell the truck in front of me.....

I just have to be careful to remember to but it back on "vent" for a while or you wind up with "AC funk" as discussed in many other posts.

 

Think of AC as climate control, not cooling.

 

Mitch,
You will find that you need to force it to 'floor/defrost' to keep the windshield from fogging in the fall and Spring, maybe winter too. IMO, it SHOULD be the automatic position any time the outside temp is 40F or below, maybe even 45F. I don't know what the set point is for the computers but it is MUCH too low. I really wish this set point was customizable.

So, you can hit the Auto A/C on the wheel, then the Climate button on the MFD surround, the the Floor/Defrost on the MFD. It will still manage the temp and fan speed for you.

 

Mitch:

Also remember that the car relies upon "recycled" cabin air to cool the traction battery (that's what that mysterious vent by the right rear passenger's shoulder does). Though it may not be a huge issue in your climate, trying to "sweat it out" to save gas as you might do in a conventional car, can turn counter-productive should the TB get too hot. The ECU will act to protect it if it does, and the result will be an mpg hit. I'm with the set it and forget it group. Just use the temp settings to moderate it (and occasionally mode too), and you'll do fine.

 

So let me see if I understand this...if I turn off the A/C when in "Auto" mode then the system will still still try to meet the target temperature....right? What happens when you are not in "Auto" mode and have the A/C turned off...does the system still try to meet the set temperure?

The Owners manual entirely skips how the system operates when not in "Auto" mode.

 

In manual mode you have to manually set the fan speed and vent settings. There is no temperature setpoint in fully manual mode.

Tom

 

Thanks Tom...if that is the case what air comes off the fan..hot? cold? If the temp setting doesn't do anything in manual mode how does the car know if you want heat or not, just from fan settings?

In an older conventional car there is a manual heat setting, non thermostatic, that regulates how much air passes through the heater core.....Does the Temp setting on the Prius also determine the amount of air passing the heater core ( or regulate the temp of the heater core itself?