Heating/Cooling Questions...

I don't (yet) have a Prius, but the Climate control of my car (a VW Polo) is very similar. When I hit AUTO, the system decides how to cool/heat the cabin, adjusting the mixture of the air. It also uses the A/C to de-humidify the air (even when heating, the A/C is working to prevent the windshield getting steamed up). Then I can press the ECO button (or disable A/C in the Prius) and it will try to do it's best without using A/C.
Also in AUTO mode it will decide where the flow will go to. Usually, when heating, it will direct it to the feet and to the head when cooling. If you change the direction of the flow or the power of the fans, it will disable AUTO mode.

So, if you want air to the feet and heat, you can choose it with the MODE button, adjust the FAN speed and hit A/C if you want it. Then the climate control will adjust the air mixture to the desired temp and blow it where you want.

I don't know if this helps you or confuses you more!

 

There's no way to set the fan speed of Auto mode though is there? Auto comes on full blast, upper vents only at first. I hate this- it feels like I'm being chemically air dried or something. If I press a fan button or switch vent mode it kills Auto. I'd like to stick to the steering wheel controls rather than adjusting on the console. ECO mode helps, but I don't like to drive with it on in the city.

 

I would like to see auto mode allow you to set preferences such as maximum fan speed.

Roy

 

If you select auto then you are giving the car climate system full control over the air conditioning and it will decide how best to work that system in order to achieve the temperature you've selected.

My last car was a Lexus and the climate control system sounds the same. Full blast is just the fastest way to circulate the air in the cabin and therefore get it cooled down to the desired temperature, so that is what it will go with if you use auto. Once it achieves the temperature you want it will lower the fan to the level it needs to maintain the temperature selected.

 

When using AUTO the fan speed is set partially based on the temp difference between the set point (the temp you have told it you want it to be) and the actual temp (the temp it currently is). If the differential is several degrees the car will work harder to get to the set temp... i.e. the fan will blow harder. Just raise or lower the set point to match and the fan will slow.

For example if you are trying to cool (the inside temp is warmer than your set point) in AUTO... try raising the temp set point a few degrees and the fan will slow. Reverse that when trying to heat the cabin.

Or you could just be patient and once the car cools/warms the fan will slow automatically...after all it is the automatic setting.

G

 

I had the same questions as the OP - even though their appears to be a difference of 15 degrees between the temp I set it to and the outside temp, it still seems like it won't engage the AC when set to Auto - it just blows the outside air on high. I wouldn't mind this as much if it would at least engage the AC (would the light come on if it did?) though I also agree that I would have liked to see a max fan speed option.

The outside temp seems to be a little high (~5 degrees maybe?) from what I am reading using other thermometers. Also, is there a way to see what the car thinks is the inside temp?

 

So, to get heat, just set the temp where you want it, and mode to feets or whatever?
Can you force A/C OFF, if it's dry and cold?

 

Yes, if you want to operate the Heater manually, you can select the Temperature, the Mode and even select the speed you wish the Fan to blow.

Anytime you don't want the A/C ON, you can press the A/C button and disable the A/C.

However, it's much easier to simply select the Auto Mode and let the system manage itself, but you must remember, that pressing ANY button other than Temp (Fan, Mode or Vent/Recirculate) will disable Auto and revert back to manual.

Also, when in Auto Mode, and starting the system for the first time on a hot or cold day, the Fan speed will be accelerated to raise/lower the temperature to your set temp. However, that Fan Speed will begin to slowly reduce, once the interior temperature begins to match the temperature you have set.

David (aka Blind Guy)

 

Took my week old Prius into service today as I couldn't get the auto function to cool the car. It just seemed to be blowing in warm air. However when I collected it, they advised me that all a/c functions were operating correctly. After a bit of experimentation, I realised that you have to have the a/c button on all the time if you want to use the auto function. I can't get my head around this. Surely the purpose of the auto function is to maintain the selected temperature automatically switching in fans / ac / heater as required. It certainly has in all other cars I've owned.

Reading the user manual (UK version) one page states that pressing the auto button will operate the a/c but another page contradicts by saying that a/c does not operate even of auto is pressed.

 

I was driving my wifes Prius and I kept decreasing the temp and the interrior was not cooling down. I told her the AC does not work. She told me the AC button has to be on for AC. I guess that makes sense???? I have had several cars with auto temperature and this is the only one that I have to turn the AC on when setting the temperature. It is not a big deal but I believe if the auto feature is set at 72 it should cool the inside of the car down to 72 automatically. I am thinking about labeling my "AUTO" button "Sort Of Auto".

 

I can't think of any car or truck that I have that does not require the little AC light to be on for the AC to function. Really it's that simple

 

Think of the AC button as an "enable" button. The Auto mode will call for cooling including the use of the compressor without any intervention from you. Leave it alone other than to set the desired temp. Many people think raising or lowering the temperature to the max extremes is what they have to do, but don't do it, just set the desired temperature. It is designed similar to commercial building HVAC systems using Variable Air Volume control which is very efficient and achieves better temperature control than a "nervous Nelly" constantly playing with the controls. Once the initial cool down or heat up is achieved, the system will throttle the air back to a low level or just enough to maintain the set temperature. The solar sensor will detect high solar loads and keep the air flow higher to maintain the desired temp as well. What you can't see or hear is the compressor being modulated to achieve the necessary discharge temperature depending on load. Also, in the ECO mode, the AC is limited to a lower level of cooling to save energy and fuel and will stay in the recirculate mode longer than in Normal mode. Any attemp to intervene is going to cause the sytem to revert to manual mode. The only time to make a change is when you need to defog the windshield and side windows, and even then leaving the AC enabled will keep them clear except when there is frost on the windshield.

The bottom line is you bought an automatic system, just let it do its job. you can adjust the vents to direct the air flow where you want it so don't obsess over how you think it "ought to work"..... Oh and by the way, don't take my comments as criticism, just offering an explanation of how auto sytems like this one work.

 

Gil has it right. The problem is that many people think of the A/C button as an on/off switch for the compressor. It's not. When A/C is off, the compressor can't run. When A/C is on, the compressor will run only when needed, and then only at the required speed.

An earlier poster asked if they could turn off the compressor when it is cold and dry. The answer is yes, but you don't need to. The Prius is smart enough to not run the compressor when it is not needed.

Most of the complaints about the Prius climate control system come from people fighting the system. If you let it do it's thing, it works well and is easy to use. Put it on auto and adjust the temperature to your liking. The Prius will do the rest.

Tom

 

I hope this will help. After a week in mine, I noticed the same "problem" and I spent the next 2 days trying to understand the logic behind the apparent lack of a functioning AUTO climate control system. My rationale was essentially the same as yours--I have a newer Honda and Lexus--both have auto climate as well, but they will cycle the A/C as needed to maintain the preset cabin temperature with no intervention other than the initial pressing of the auto button. Can this really be differnt??

I expected this system to work the same way. However, I found that regardless of how many times I turned the system on and off, the AC would not start even if the cabin temp was far higher than the setpoint. I assumed mine was faulty as well. I took it in to the dealer and we tested another one just like mine, and the AC was immediately on when we first engaged the AUTO button.

A little more research showed that Toyota changed things a bit with this car. If you push the AC button ON (little green light is illuminated) after you push AUTO, the AC will keep the cabin at the temp you desire (assuming it is cooling due to higher outside ambient temps). If you then turn the system to OFF for awhile and back to AUTO again, the AC will automatically be on (illuminated again). But if you turned the AC off, the regardless of how many times you cycle the AUTO system on and off, it will always stay off.

As far as turning the car off--if the AC was on and AUTO was engaged and the car was turned off, the climate control system will turn back on by itself again when you start the car up and the AC will still be illuminated and operating. (This is what happened to the car I tested at the dealership). If the AC is on and the system in AUTO but you turn the system to OFF before turning the car off, then when you turn the car back on again at a later time, the climate control system will still be OFF. However, once you push the AUTO button, the AC will again automatically come back on.

So, yes, it is a SEMI AUTO system in that respect--it forces you to intentionally turn on the AC if it wasn't on the last time you were in the vehicle. This is a different approach for Toyota, but it is all in the name of fuel efficiency. In "normal" vehicles, the AC runs much more frequently than it really needs to, burning extra fuel needlessly. This is just another way Toyota is purposefully trying to reduce uncessary fuel comsumption (and comensurate emissions) in this vehicle. It may be aggravating at times, but it does play a part in my 80+mpg 14 miles stints home from work each day. If I"m not paying attention to the AC, it can get warm in the cabin--but that may also be from my beaming internal pride from using less fuel than my fellow roadmates.

 

Thanks for the explanation. This AUTO/AC thing has been bugging me since getting the car. You're right. It's a Semi-Auto system.