climate control--can you help an oldster understand?

<div class='quotetop'>QUOTE(goldprius @ Aug 2 2007, 06:48 PM) [snapback]489709[/snapback]</div>

Welcome to Priuschat.
As a partial answer to your question I am attaching a write-up by Tony Schaeffer who puts it much better than I could.
"Toyota's use of the term Air Conditioning in the Prius is technically correct, but many drivers confuse Toyota's use of the term with the common belief that Air Conditioning refers only to the cooling of cabin air.

The light on the dash indicates Auto A/C. If that light is on, the system will make all the decisions about air volume, air output, air source, compressor status and heat status based upon the temperature setpoint that is changed either at the steering wheel or on the MFD. The Prius system is fully automatic and behaves the same as nearly every other automatic climate control system I have ever used.

Now, with the light on, if you go into the MFD and start adjusting the system, the Auto A/C light will go off. That means that the system is not fully automatic anymore. Starting at Auto A/C, as soon as you manually adjust the fan speed, the system will not be able to adjust the fan speed automatically. That is why the Auto A/C light goes off. Not because the system is not going to run the A/C compressor, but because it is not fully automatic anymore. The same goes for air output, if you manually adjust that from the Auto A/C light, the system will not be able to choose the air output.

The temp setting does as it indicates. Its goal is to keep your cabin at the temp you indicate. It will heat as necessary and use the compressor as necessary to achieve these goals.

There is an A/C button on the MFD in the upper left corner. I call that the A/C defeat switch. If the yellow bar at the top of that soft button is on, it means that the automatic system has access to the A/C compressor. If you press the A/C button and the light goes out it means you have told the system that it may not use the A/C compressor. This light does not indicate when the vehicle is using the A/C compressor. You have no direct control over when or how the system uses the A/C compressor. You can adjust the cabin temp up or down, but that is the only control you have aside from the A/C defeat switch. 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.

Additionally, the compressor is not on or off, as in most cars, but is variable speed and runs at speeds necessary to provide the appropriate amount of cooling to the system. In the summer, as the cabin cools down the compressor will slow down. This is a significantly more efficient A/C design than in conventional vehicles in which the A/C compressor is engaged or not engaged and nothing in between. You should also be aware that the A/C compressor is electric and as such does not load down the engine with a high demand pulley accessory. Instead all of the energy used to run the compressor comes from the HV battery and electrical system.

I have discovered that I loose only a couple of MPG in the summer with the A/C, if that much. As such I do not consider it a sufficient loss in MPG to choose to go without A/C. And considering the additional benefits of running the A/C (circulation of oils, battery cooling), there is no question that the auto A/C system that Toyota put on the Prius is there for a reason and is as integrated into the vehicle's operations as the HSD system."

 

At this time of year, where I live, it is comfortable to shut the AC off on the morning drive to work, but AC is mandatory at lunch time and later in the day.

So in the mornings, I hit the Climate button next to the MFD, choose a fan speed that I like, hit the button that sends the air to the dash vents (if necessary) and then turn off the AC with the button in the lower left corner.

At lunch (if I drive the car) or later in the afternoon, I just hit the Auto AC button on the steering wheel to turn the AC on again.

 

Used to play with climate control screen all the time, but I finally decided that Fiona is smarter than I am so I just press the AC button on the steering wheel & let her do what she will. I do adjust the desired interior temperature from time to time, and I religiously turn the AC button off when I am gliding into my garage at the end of the day (and each time I park on intermediate trips).

 

<div class='quotetop'>QUOTE(Grandma Judy @ Aug 3 2007, 10:50 AM) [snapback]489914[/snapback]</div>

This is just what I do. Just set it (at 75 degrees) and forget it.

If you use the air conditioner most of the time, you really don't need to turn it off. The Prius' compressor is electric and thus places no load on the ICE.

 

<div class='quotetop'>QUOTE(goldprius @ Aug 2 2007, 07:48 PM) [snapback]489709[/snapback]</div>

I tried to do that when I first got my Prius, then gave up. When I opened it up to fresh air with no AC and temp to lowest, it blew warm even if it wasn't that warm outside. It's such a hastle to do that too... too many buttons to push, also you must move temp all the way to low. Now I just leave it on auto or off, open the windows if I don't want AC. Ahh, for the days of mechanical levers to push!! Some things shouldn't be computerized for the sake of computerizing it... like books for instance! When was the last time you had the battery run down on your paperback or dropped it and broke it?

 

Having the windows open at speeds greater than, say, 40 MPH, will give you poorer MPG than using the A/C with the windows up. Press the "recirc/outside air" button to select "outside air" if you use A/C and want to ensure you get "fresh" air (you are assuming the air outside is fit to breath - this is less and less probable as we "advance").

I installed the air deflectors that go at the tops of the side windows, because here we don't need A/C for more than a few weeks of the year. Many of you southerners would say never - a "hot day" for us is 30C (86F), though last year we did hit 40C - once. Anyway, this allows me to leave the side windows down about 1-2" without the worry of getting rain or dew inside. Still noisier than windows up, and I wouldn't do it on the highway. I use A/C auto when it's warm and fan on "4" when it's not.

 

Remember that the A/C is not just there for our comfort, it's there to keep the HV battery happy to, the battery works best when it's not too hot or too cold. I'm pretty sure that's why the car has computer controlled climate control as a standard feature.

 

<div class='quotetop'>QUOTE(lowlander @ Aug 3 2007, 12:27 PM) [snapback]489975[/snapback]</div>

Well I thought I understood how to work the climate control in my car but now I'm confused.

Are you saying that I can't be warm in the winter because the battery will be uncomfortable? Because I have real problems with the cold and I want the heater on full blast in the winter.

When outdoor temps are in the 70s and I'm on local roads driving 30 mph, I don't want cold air from the A/C blasting on me, I want the windows open so I can feel the breeze. So I leave the A/C off, make sure the temp is set below the air temp, and leave the fan on low.

Sometimes during long afternoon drives the car can get warm inside even when it is in the 50s and 60s outside. But in these cases I don't want cold air blasting from the A/C because that's too much. With my old car I just turned the air temp dial all the way over on the blue side (coldest setting), turned up the vent fan and the car would be comfortable using outside air only. I plan to do that with the Prius when the weather gets cooler again.

At first with the Prius I had the Auto A/C on, but I found the A/C would come on and blast cold air on me when I didn't want it, so I turned it off. Now if I want A/C I turn it on, and if I don't feel it's necessary I turn it off. If I am comfortable (not hot and not cold), I fail to see why the battery should have a problem. If it needs extra cooling there should be a mechanism for that that is separate from the climate control for the people in the car.

 

So I should not be driving with the climate system off and the windows up and the cabin temperature between 100 and 110 degrees F ? :huh:

 

I just set my climate control to "auto" and set the temperature to 75.

I don't like cold air blasting at me either so I turn the vents to blow elsewhere.

 

Thats the whole reason I don't use the Auto Feature. I like the air blowing at me I just don't like it blasting at me.

If I leave the setting on Auto A/C at 75 degrees and it is over 100 degrees outside the AC blows at me at the highest possible speed.

I usually put the fan on level 2 or 3 and set the temp between 75 and 78 degrees and it get the job done great.

 

<div class='quotetop'>QUOTE(bmwquickspeed @ Aug 3 2007, 03:39 PM) [snapback]490090[/snapback]</div>

I'm amazed by how cold the AC gets. I end up putting it on 78 after it gets cold in the cabin, otherwise I get too cold at 75. It works very well. I used the "vent" setting in the spring, it's not that hard to do. My last car had auto air also and never got as cold as this one and putting it on a "vent" mode wasn't readily apparent either. Once you get used to it, it really is a matter of touching just a few buttons.

 

<div class='quotetop'>QUOTE(goldprius @ Aug 2 2007, 08:48 PM) [snapback]489709[/snapback]</div>

Just set it on auto, adjust the temp. to your liking, then sit back and enjoy the ride.

 

not sure if this is how it works... but for me, I would think that selecting a temperature, even say 85, would cause the heater to kick on... but in my car, it does not, I have to set the temp to something high, then turn the AC button off, and then the heater kicks in instead. Kind of strange, is that how it is designed or is my system all weird?

 

<div class='quotetop'>QUOTE(YodaddyAlex @ Aug 8 2007, 08:09 AM) [snapback]492393[/snapback]</div>

That is not how it is supposed to work. Either your system is malfunctioning or you do not wait for the engine to warm up before you start messing around with the controls. In the heat mode, the fan does not start blowing until after there is warm coolant. When you manually raise the thermostat, electric coils are activated to supplement the engine produced generated heat.

 

For defrost, press the button on the lower right side of the steering wheel. There are 3 of them, one is for recirculate/fresh air, one is for windshield defog/defrost, one is for rear defrost / heated mirrors. The one for the windshield defog/defrost has a symbol that is wedge shape with the wider part at the top.

For more info, see Section 2-9 in the owners manual.

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