Is the a/c designed most efficient when permanently on?

Discussion in 'Gen 2 Prius Main Forum' started by Bronze84, Nov 21, 2013.

  1. Bronze84

    Bronze84 Member

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    On my old Lexus, the a/c was similar to the Prius in the fact it was digitally controlled. I left it on all year round as it didn't really effect fuel economy and it seemed fairly efficient.

    Now that winter is drawing in I'm using front window demisting quite a bit. Every time it is put it on though the a/c comes on with it. I appreciate it can clear the window more quickly with it on but it's really annoying that I have to turn it off all the time.

    It's made me question whether I am using the a/c in the most efficient way? Is the system designed to be left on? Also does it get it's power from the HV battery or from the engine? As the hybrid set up as a whole seems to be quite delicate with changes to things such as outside temps, heating the car up etc, I don't want to effect the economy too much. Ideally I think the answer I'm hoping for will be to leave it on and forget about it :)

    Cheers, Martin


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  2. dorunron

    dorunron Senior Member

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    I believe that the Prius uses LESS energy whenever the A/C compressor is turned off. Since it does run off of the traction battery, it ultimately will use more fuel which will lower MPG.

    I keep ours turned off unless I want actual A/C.
     
  3. Britprius

    Britprius Senior Member

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    Martin, I think there is an option on the gen2 via Techstream to turn the AC off by default when you demist the screen instead of it coming on all the while. If I get chance in the next couple of days I will check it out and advise.
    If this is possible I will be doing this to my car.

    John (Britprius)
     
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  4. Britprius

    Britprius Senior Member

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    Another thing to look at in the way of modifications is to fit heated mirrors. This is not difficult or expensive. If you are interested let me know.

    John (Britprius)
     
  5. vskid3

    vskid3 Active Member

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    All the power for the car comes from gasoline, so the AC will lower your mileage. I would use it as little as possible. However, safety comes first. If your windows fog up without the AC, you should use it.
     
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  6. Britprius

    Britprius Senior Member

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    Martin.
    There is a setting for the AC as I thought if you have the Mini VCI and Techstream or other suitable device.
    Go to AC / utilities / compressor, choices are "auto or manual" default is auto change to manual and save.
    This setting may revert to auto if you disconnect the 12 volt battery (have not tried this).
    This stops the compressor starting unless you select AC on the touch screen.

    John (Britprius)
     
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  7. FreydNot

    FreydNot Member

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    Anybody know the actual codes that Techstream is sending to achieve this? I would love to use Torque to change the setting. I have successfully used Torque to disable the reverse beep in a gen3 Prius I was renting. I would suspect this would be similar.
     
  8. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Just to mention, it's worthwhile running the a/c at least a few minutes, say once a month: to keep oil in the circuits circulated.
     
  9. Armacham

    Armacham New Member

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    I did notice that on the climate screen, while on AUTO, the A/C button is lit even if I am running the heater. Is the compressor actually running or is the computer just telling me that it will run if I ask for cold air, or turn on the defroster?
     
  10. Britprius

    Britprius Senior Member

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    It runs even if you are asking for heat. It is there to remove moisture from the air.

    John (Britprius)
     
  11. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Yes, that's the idea John. You got it.!!!
     
  12. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Yup, it will run at the most efficient load. Since it is electric, the compressor can run at any speed, therefore only at the required load. It can run full blast even with the gas engine off.

    This is superior to any belt driven compressor chained to a combustion engine.
     
  13. Data Daedalus

    Data Daedalus Senior Member

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    I've been following this thread and I'm now puzzled about something - my Prius used to turn on the A/C by default when ever I hit the front windscreen demisters. Though I was not happy about the resultant MPG I perceived, I was grateful for it on those few frosty mornings recently when I needed to defog my front windows, however, I digress.

    On one such occasion while commuting to work, I was pleased with the powerfully efficient way the Climate Control had rid the interior of the windows of all traces of fogging, I then disabled the A/C side of the equation by turning it off from the screen - apparently while the front demisters were still lit.

    I turned that off from the steering independently sometime after that. And here's the curiosity; since then, when I press the front demister switch on the steering, the A/C doesn't come on! I must however concede, this might be because I already have the standard blower (without A/C) on - before I lit front and rear demisters.

    Anyway, all of this week - the A/C hasn't come on - and yes, I've been using that front windscreen demist button. I'm surmising that some how I've turned it off from being initialised by the front demister button on the steering wheel. I'm sure my A/C still works though. I'll check it on the way home in a moment.

    I am still discovering the complexities of my wonderful "Futurama-esque" Prius II T Spirit, suffice to say it never ceases to impress me, even after 5 months and 4,700 miles of ownership. It has easily surpassed all the positive expectations I ever had for it. Impressed, I definitely am :D


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  14. Integraoligist

    Integraoligist Junior Member

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    Data, I've turned off the A/C while using the "demister".... turned the car off then back on, and the A/C comes right back on.
    How was yours working yesterday?
     
  15. Kurzweil

    Kurzweil Member

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    When I want to manually cycle the A/C for demisting, I turn AUTO on using the wheel control, go to the screen and turn A/C OFF. Then when I hit the defrost button on the steering wheel, it turns the compressor on. hit the defrosts button again and the compressor goes off with the air being redirected back to VENT. That way, I can keep the windows clear by running it for fifteen seconds or so every couple of minutes, at least until the car interior is warmer, at least in cooler weather.
     
  16. vskid3

    vskid3 Active Member

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    My front defrost used to turn on the AC by default as well, but I disabled it the other day and this morning the AC didn't turn on when I turned on the defrost. I thought it was kind of funny that it happened after reading your post yesterday. I'll let you know how it acts the next few times I use defrost.
     
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