using "A/C Auto" and other Climate controls

Maybe I'm mistaken, but you use the "up" and "down" arrows to set the temperature you'd like it to be in the cabin... So, if it's 20 degrees outside, set it to 75, and the climate system will work to get it to 75 inside the cabin (i.e., turn on the heat)... Conversely, it would turn on the A/C with cold air if it's 100 degrees in the cabin and you set the temp to 75.

This works just like your thermostat at home... You set it to a temperature, and your central air system does whatever it has to do (heating or cooling) to get it to your desired temp. More "intelligent" system than just choosing if you are a "RED" temp or a "BLUE" temp person. But let's leave politics out of this.

 

It is confusing and Toyota isn't consistent. A/C Auto will both heat and cool you to the desired temperature you set. If you hit the "Climate" button it will show you the details of the climate control system, including the outside temperature and the desired cabin temperature. If you want it warmer, set the cabin temp above the outside air temp. If you want it cooler, set the cabin temp below the outside air temp. The car will heat or cool as needed IF the AC button on the climate screen is lit (has a bright bar in it). If the AC button is lit, it doesn't mean the compressor is running, just that it can run if the cabin temp gets higher than the desired air temp. The heat will come on if the cabin temp gets lower than the desired temp.

If you don't want the compressor to run to cool the air, you can touch the AC button to make the bar dim. This is a good setting if you just want fresh air, but you also have to lower the desired cabin temp to below the outside temp or you'll get heat.

The whole idea is to just pick a comfortable temperature, set it, and forget it.

To turn off heat, set the cabin temperature lower than the outside air temp, or all the way down (MAX COLD).

To turn off cooling, set the cabin temperature higher than the outside temp OR turn off the AC button.

To set the fan at a constant speed and remove it from automatic control, touch a fan speed button.

I hope this helps more than confuses.

 

That "cabin temp" you refer to is not the actual temperature; it's the interior temperature which the car is attempting to maintain.

While the car must know the actual interior temperature, it doesn't display it anywhere.

 

This is great - I too am a new Prius owner today and was totally confused by this issue! Thanks!

 

It also helps if you think of the lesson I try to teach my anatomy students...

The nose on your face is an 'air conditioner' it warms and moisturizes the air you breathe in so your lungs don't chill, or dry out.

The AC system on the car CONDITIONS the air - to whatever parameters you set. As previously stated if you give it a set point that is cooler than the outside air it will blow cold air at you until the interior reaches that temperature (actually, probably a bit below your set point for reasons I'll not get into here involving a phenomenon known as negative feedback).

So, in short AC does not necessarily stand for Air Cooler, though most folks think of it that way.

 

Agreed, Toyota is not consistent in the use of the term A/C. Sometimes they mean the HVAC as a whole, and sometimes they mean the cooling system that makes use of the refrigerant compressor. Most of the time, they mean HVAC.

The Prius has a very sophisticated automatic HVAC. It uses the A/C not just to cool, but also to dehumidify, so in climates that are known to be hot and humid that bacome cooler, such as here in Florida, can still be quite humid and uncomfortable. That's why I often still use the A/C even when it is cool outside. Stinky diesel engines out there is another reason.

The HVAC has three main operating states: Full auto, where it will heat or cool as necessary, heat only where the A/C is turned off and only heat is applied if needed, and Off. Unfortunately, Toyota neglected the Cool Only as one has in their house in the better thermostats.
In full auto, and even in limited auto where some controlled items are manually controlled by you, the system takes 5 inputs:
Existing cabin temp, desired cabin temp, cabin humidity, solar radiant heat (note the sensor by the windshield on the left side of the dash) and outdoor temp. Using those, the car determines AC compressor speed (it is continuously variable), fan speed, application of heat, recirc, and duct selection to achieve the cabin 'Feels like' temp you selected.

 

Another quick note: if the cabin is hot, the AC will run the fan in Tornado mode (really high fan speed). This is to cool the cabin quickly. As the cabin approaches the desired temperature, the AC will move the fan to slower settings until you about can't hear it. Very smart system. You can override any fan speed on the climate page.

Robert

 

DanMan is spot on with his description of Prius climate controls and his opinion of the terminology that Toyota uses to describe them or their function. There is a great deal of inconsistency in terms of using A/C to describe the act of cooling air for the cabin and the use of A/C to label the system as a whole.

However the North American driver is used to a/c not being a general term for all forms of air conditioning, which include heating air, cooling air, filtering air, humidifying or dehumidifying air, etc.; rather we are used to a/c being a button with the air handling controls, or a spot on the air duct slider where we get chilled air coming out of the dash to make our vehicle comfortable. I think our limited definition of a/c can be attributed to the fact that for most of the time a/c has been available in cars, it has been an option and not standard equipment. That has changed significantly in the last 10 or more years. Basically everything that a fully equipped home or commercial HVAC system can do is air conditioning in the widest definition. So the way Toyota describes the Prius system is fairly accurate.

We are finally at a point in auto development where "air conditioning" can be used to describe automobile air handling systems because they include most of the features of a good home system, including air cooling, heating, and air filtering with thermostatic control to maintain environment temperature.

As for how I use the system in the Prius, aside from some temp adjustments from season to season; I set it and forget it.

 

Is there any way to run the A/C compressor while adding heat?

I used this technique many times with my previous car ('97 Camry) when it was cool and very humid. The windshield would sometimes tend to fog up (even using fresh vs. recirculating air). The A/C (cooling) would take the moisture out of the air, and the heat would bring it up to a comfortable temperature.

I haven't run into this situation yet with the Prius, but would like to know in advance.

Thanks

 

The front windshield defog setting works this way.

 

The only weird thing about the heating/cooling system is if the temp drops down to freezing just as you start your car the condensation can escape off of the Air Conditioner and freeze on the windshield. Make sure you don't leave the defroster on as the engine stays on all the time. When I park it at night, I usually turn off the Air as its outside and gets a litlle cool at night now. Here's 3 points to keep in mind as the cold weather barges in:
1) Just leave it on Auto as the car knows when the engine is warm and slowly ramps up the fan as the engine heats up. If you turn up the fan before the heater core heats up you'll get constant cold air, because it'll keep the heater core cold.
2) Keep the toneau cover closed as it's less area to heat.
3) I used the defroster 5 times last winter. The windshield stays remarkably clear even though its huge (compared to the other cars I've owned or own now). I try and leave the windshield cold as it's easier to clean off the snow.

Hope this helps.

B)

 

Thanks Phil,

I found that the front defog heats the external mirrors, but we haven't had weather that fogs up the windshield yet.

Thanks again

Norm

 

Two questions:

1) Norm mentioned that the front defog heats the external mirrors. Is this standard or only in certain packages? I have this feature on my Ford Exploder and it is a really nice feature to have during a Michigan winter. I didn't think I had it on the Prius. We have package 4.

2) Our Toyota salesman told us that one of the features of the Prius is "instant" heat. He told us that there is a thermos type of device that stores the hot water for up to 3 days. So when you start the car in the morning, you have heat "instantly". It hasn't got terribly cold yet but I haven't noticed "instant" heat either. What's the truth?

 

Well, "instant" is a bit of a misnomer, but he's not lying to you. Primarily to heat the *engine* to operating temperatures faster (and thus get the emissions system up to spec), the Prius does have a small thermos that stores hot coolant after the engine is turned off. The thermos can keep the coolant reasonably hot/warm for a day or two. When you turn the Prius back on, it pumps this coolant into the engine to "pre warm" the engine block -- though it can't possibly get it back up to operating temperature instantly. As I said, this is primarily for the emissions system, but since the engine is used for heating the cabin, it helps temperature control, too.

The problem with heating the cabin air and the hybrid design is that the engine doesn't always run -- taking away your heat source. To counter this, the Prius includes an electric heater to help warm the air when the engine is too cold or isn't running.

It won't be "instant" heat, per se, but it (in theory) should be better (and at least not significantly worse) than what you'd get from a regular car with its engine cold.