AC & heat controls

Discussion in 'Gen 3 Prius Main Forum' started by jediatzinger, Oct 30, 2013.

  1. jediatzinger

    jediatzinger New Member

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    I have a 2013 Prius that's just a few months old. I absolutely love driving this car. I have a couple questions (now that it's starting to get cold) about the AC & heating controls.

    #1 - Vent
    I think that if I ONLY press the fan speed (+) or (-) without anything else this IS the vent - correct?

    #2 - Inside/Recirculating airflow
    One of the controls shows airflow coming in from the outside or recirculating. What should this be at for optimal mpg? There is also a control for this on the steering wheel, which makes me think this is important. When and why would I want it set a certain way (inside vs. recirculating)?

    #3 - Misc
    I do not use the "auto" setting. I've read that's not ideal for good mpg. I have the temp set to 70 and if it's 65 outside I'd really just like to let the outside (cooler) air in, which is where I think the vent setting would come in handy, but wouldn't I also want to have the airflow set for outside vs. recirculating... what I don't want is for it to "heat" the temp up to 70!

    I've noticed that the Prius somehow knows to use the floor vents and/or the dash vents (top/bottom), but I've never pressed the button to make a choice. It seems to just do it on its own, which so far has been fine :) Is this normal?

    Thanks - I'm still working the green (noob) out of me, but this car is awesome.

    NOTE: I'm just now getting to 4k miles. I thought I read somewhere (on here) that I should change the inside air filter (behind the glove compartment). When should that be changed?
     
  2. tumbleweed

    tumbleweed Senior Member

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    The short answer is put it in Auto and set the temperature where you want it and it will be fine. You can still turn the AC on or off while in Auto. You may also need to turn the defroster on or off. Leaving the climate control in Auto will not have a noticeable impact on mileage as long as you don't have the AC on and the temp set to super cold.

    There are some older posts here where we discussed the Gen 3 climate control settings in excruciating detail but you will most likely need to use Google to find them if they still exist. There is also some limited information in the owner's manual.
     
  3. BZzap!

    BZzap! Senior Member

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    You might note that when in "Auto" mode the system will default to "Recirculate". This is so the cabin air is not blended with outside air. The purpose is to make optimum use of the HVAC system to keep the A/C compressor and ICE from operating trying to keep up with outside temperatures.
     
  4. jlim888

    jlim888 Member

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    I read in the other thread that if you are in "recirculate" mode with AC on, the air could develop musty smell... so I either move it to "outside air" mode or I turn off the AC a few minutes before I reach home.

    This musty smell isn't Prius specific, my other cars have the same musty smell if the vent is left in "recirculate" mode with AC on for a long period of time.
     
  5. BZzap!

    BZzap! Senior Member

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    If the evaporator drain is clear I don't see this as a problem. Most of the time when a musty smell developes it is when water ( condensation ) gets trapped in the evap. housing.
     
  6. David Beale

    David Beale Senior Member

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    Adjusting fan speed will turn on the fan and set it at the speed indicated. It will also turn on A/C sometimes. A/C means air conditioning, meaning heating or cooling, as required. Set your desired temp. If you set it to 65F and it's lower than that outside it will only blow outside air into the car. Until the car gets too cold, then it will heat the air. Use "Auto" for best results.

    In winter you absolutely want outside air. This is to decrease the humidity in the car so the windows don't fog/ice. If you use "Auto" it will not decrease the mileage noticeably. It will start on recirc. but will then go to outside air when ready. If you turn on defrost (front) it will run the A/C (cooling) to dry the air and will use outside air. It will heat the air and blow most of it on the windshield.

    The cabin air filter is behind the glove box. Empty the glove box (if you don't it will empty automatically on the floor when you do the rest here ;) ). Open the lower glove box, press the sides in so the little "ramps" clear the dash, unhook the "damper" and the glove box will pivot down out of the way. You can see the filter on the firewall. Pull it out and look at it. If it's plugged clean or replace it. If not put it back in and replace the glove box.
     
  7. southjerseycraig

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    I *think* this is true only when you have the air conditioner on. I find that I don't need recirc past the first five minutes or so, and I usually turn it off. For some reason, the fan becomes less noisy when recirc is turned off.
     
  8. macman408

    macman408 Electron Guidance Counselor

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    No. It will still try to control the temperature to whatever the setting is. The only way to guarantee pure "vent" is to set the temperature to the lowest setting, turn the A/C off, and ensure that the vent is not set to one of the defrost settings (which turns A/C on, even though the light stays off). In general, any time the temperature is set to lower than the interior temperature and A/C is off, you get vent - the max lo temp setting just covers the case where it's already really cold in the cabin.

    I think usually it's most efficient at recirculate, assuming that the interior temperature is closer to the desired temperature than the exterior temperature is. (In other words, if your car was baking in the sun at 150°F and you turn on A/C, you're better off on fresh air for a few minutes, until the interior temperature is below the exterior temperature again.) In cold weather, recirculate keeps all the humidity from your breath in the cabin, so it's often preferable to use fresh air, which is drier and won't fog up the windows as easily. Once the car has had time to fully warm up, heating with fresh air won't make a difference, since the excess heat is a waste product otherwise.

    Assuming you just set Auto to whatever temperature you can tolerate (and disable A/C if you don't need it), it will be more efficient than many ways you might manually manipulate it; for example, setting the temperature to 68° with A/C on and the fan on 1 bar is way less efficient than setting it to 78° on auto with the A/C on, even if the cabin temperature is 68° in both cases.

    If you want to let cool air in, just turn the temperature down below what the temperature is inside. In your example, if the cabin is 80°, it won't heat at all, even though the outside temperature is lower than the set temperature - the set temperature is a goal for the cabin, not the temperature that is coming out the vents. On the other hand, if the eventually drops to 69°, then the car will add a little heat to keep the outside air from cooling it below your set temperature.

    Bottom line; just set the temperature to whatever makes you comfortable. Bonus efficiency points for leaving A/C off, and for leaving the heat off until the car is fully warmed up - this may take 20 minutes or more. (I live in a mild climate, and it takes ~4-6 miles of city driving, or maybe 2-3 of highway driving, when outside temperatures are around 50° or so.)

    Heat goes to your feet, cooling goes to your face, and defrost goes to defrost. This is generally preferred - otherwise heat to your face leaves a big pocket of cold air at your feet. On the other hand, my face and hands are more sensitive than my feet, so sometimes I don't care if my feet are frozen solid...


    If you have the solar ventilation system, clean it every 10,000 miles, and replace it every 20,000. If you don't, clean it every 15,000 miles and replace it every 30,000. That's what the manual recommends, anyway. If you use the climate control a lot, or in very dusty or dirty places, it might need it sooner. If you don't, then the recommendation may be more often than you need to.
     
  9. Tideland Prius

    Tideland Prius Moderator of the North
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    If you truly want manual mode, you'll have to press all the buttons (fan speed and MODE. See the response below re: the Prius knows when to use the floor vents and/or face vents)

    Fresh Air setting. If you set to recirculating, you will need the A/C to dehumidify the air as there will be moisture from your breath and melting snow that will cause the windows to fog up if you recirculate without A/C on. Note that the cabin will heat up faster in recirculate mode.

    Set the temperature lower. Even at 70, there will be some heat once the engine's warm (but I assume that's what you want? Just some heat whenever the car has some to spare rather than forcing the car to heat the entire cabin).

    Yes. If you exit from AUTO mode by pressing the fan speed, MODE is still in AUTO mode. Vice versa, if you adjust the MODE to get out of AUTO mode, the fan speed is still in AUTO.


    Check regularly and whenever it's dirty. It depends on the air quality of your area (dusty due to sand? smoke due to forest fires in the summer? plastics or oil refineries?) and whether you have the Solar Roof option and use it in the summer.

    Depending on where I've lived, good air quality (coastal air with rare poor air quality episodes) has gotten me a year's worth (about 18,000km) but where it gets cold in the winter (-30°C for days, trapping pollutants close to the ground), oil and plastic refineries within city limits, dust from sand use (instead of salt and they don't clean all of the sand in the summer) and more diesel vehicles, I've gotten less than 6 months before the filter is clogged.


    TBH, I'd just set the climate control to 68 in AUTO, and use the car's ECO mode to reduce climate control electricity use. I've had the engine shut down at -10°C. Use the engine block heater and block your lower air dam.
     
  10. Nora

    Nora Member

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    I've been trying to remember that the recirc button is also on the steering wheel. For me, having recirc on the wheel is handy because I like to turn on recirc when I'm behind an old car with bad exhaust. Or a big dust event or some other noxious outside force.
     
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