Audo Climate Control ?

One of the best articles on this subject was written by a PriusChat member.


"Prius air conditioning system
By TonyPSchaefer
Let me tell you that I was impressed with the Prius air conditioning system right off the bat. Working for a building controls engineering company, I immediately related with what the Prius was thinking. There are some differences in the details between building controls and car A/C systems, but the basics are pretty much the same.

Basically, it works like this: if the interior of the car is hot and you want it cold, the fan and compressors come on full-bore. On the other hand, if it's cool in the car and you want it slightly cooler, then they all come on slightly. As the temperature in the car reaches the desired setpoint, Prius recognizes that it's getting closer and adjusts the compressor and fan accordingly. In that way, it eases into the proper temperature rather than running the fan all-out and then suddenly stopping (which is what most residential air conditioners do).

In an over-simplistic way of thinking of it, think of the fan speed as the proportional difference between SETPOINT and CUR-TEMP. For example:
SETPOINT=65º and CUR-TEMP=90º creates a high proportional difference resulting in a high fan speed.
SETPOINT=65º and CUR-TEMP=70º creates a lower proportional difference resulting in lower fan speed.
The Prius most likely recalculates several times per second (I'm guessing)

Secondly, you might notice that the vents blowing the air change. Rather than blowing a bunch of air out of the dashboard vents and straight into your face, Prius will adjust so the air is coming out of the windshield vents and at your feet. As the airflow rate decreases, Prius will reroute the air to the vents. This is very smart since the sensation of comfort is a combination of temperature and air movement. Doing this, Prius can keep you comfortable simply by moving air, chilling it a little less and using less energy.

Just like the variable transmission, you can think of the A/C as a variable system. Basically, if allowed to do it's thing without human interference, it will work extremely efficiently."

I don't remember who to attribute this to, but it is good info.


"[FONT='Times New Roman','serif']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"[/FONT]

 

There are a few threads on the topic already so a quick search will yield immediate results.

The defrosters are not automatic except for the rear defroster timed cut-off. Turn the defrosters off and on as you need them -- the car won't do it for you (lots of reasons for this).

Many Prius drivers refer to "A/C" as "automatic climate." Set the temp and the car takes care of when to switch from heat to cold, cold to heat, and the fan setting. Airflow is automatically outside air unless you switch it. It might stay on inside air if you already have it switched to that but I'm not sure.

Sometimes folks want more or less fan speed and they fiddle with the fan speed settings on the MFD. Most PCers will tell you to avoid that temptation and just set the desired temp up or down to make the fan speed higher or lower. It takes a little bit of getting used to but it allows you to adjust everything from the steering wheel.

Adjusting for inside/outside airflow is adjusted for one other purpose. Many people don't like the MPG when using the A/C to cool the car in hotter weather. The object is to turn off "AUTO," make sure outside airflow is selected, and adjust the fan speed/windows until you are comfortable. This avoids using the compressor and helps maximize MPG. I don't always do this because I don't like loud traffic noise coming through the open window and using vented air only cools you down so much until it is a losing battle.

 

OR, the short answer. Yes, you do not have to set anything but the temp.

In fact, some find it frustrating that you CAN'T set other things without the system arguing with you (it will change your settings sometimes, though never the temp).

Some are upset that the "A/C" light is on. The compressor only runs when the system is trying to cool the air or remove moisture (such as when you select front defrost). The compressor is also variable speed (electrically driven, not driven from the engine), so you don't waste energy when it's running.

"So relaxen und watchen das blinkenlights!"

 

I leave mine in Auto year round. I just increase or decrease the temperature a couple of degrees to suit my comfort. Leaving it in Auto almost totally eliminates any fogging of the inside of the windows.

 

One point of clarification about the defroster: When the previous poster said that the defroster is not automatic, he is referring to the all-out blast the windshield with everything you've got defrost that you get by pushing the defrost button on the steering wheel. The auto mode will never do that, but it will make a pretty good attempt to keep the windshield defogged. It will vary the fan speed and vent settings, plus run the A/C compressor as needed to dry out the air. I usually don't have to use the manual defroster button; only when the outside temperature drops abruptly or during other adverse conditions, such as four sweaty bodies and wet ice climbing gear.

Here is my simple manual for how to use the climate control system:

1) Keep it on auto. Leave the A/C enabled.

2) If your are cold, bump up the temp setting. If you are hot, bump it down.

3) Press the defroster button on the steering wheel if you can't see.

That's really all you need to do.

Tom

 

I think I'll print this out and put it on my dashboard. I easily forget and try to over-engineer the environment inside my Prius.

 

You shouldn't be driving...

 

I'm just an amatuer. Try managing the temperature in your Prius while downloading your Bluetooth addressbook, motiring your Scanguage II, and playing on LED guy's Playstation. I'm lucky to get my car unlocked using the SKS...