Auto always turn AC on when heating? How to disable it

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by hj630, Dec 8, 2016.

  1. Lucifer

    Lucifer Senior Member

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    My fourth prius, all four have had a button to turn off the ac.
    But...around 35 degrees when it rains I turn it back on or the car interior windows fog up.
    If I don't turn it off the ac is "always" running,
    It's either on or it's off.
    I certainly don't need it below 32 degrees.
     
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  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The compressor is not always running.
    Unlike 'normal' cars, where the compressor is run by pulleys off the crankshaft, the Prius compressor is electronically contolled with variable speeds so it never runs more often or harder than needed. (It could be that you are saving the wattage of the bulb on the dash) I find I like Auto, and simply do not change it for years at a time*

    * in the summer I take the mode out of Eco and run in Normal, which does change how the A/C works, even though it is not an A/C control. For completeness the Gen 1 Prius is 'normal' in this regard.
     
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  3. RXZOOMM

    RXZOOMM Junior Member

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    Thank you all for the replies!

    As an HVAC Technician, I completely understand the need to remove humidity.
    I should have mentioned I'm in So California. Fogging windows is extremely rare.

    My concern was wasting precious hours of compressor life in cool weather and the wear and tear that cycling causes.

    BTW, removing the climate control fuse under the dash, causes the radiator cooling fans to default on high speed.
    -Perhaps an indicator that there is a fault in the climate control circuit.

    I surrender!
    The wife is safe and so am I thanks to Sam's advise!
    "(And it might be an even WORSE idea to keep pestering your wife about it.) :eek:"
    LOL!
    Thanks all
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    is about the gen 2 high voltage systems.
    from 15:15 to 17:00 he discusses the A/C compressor circuits

    As the owner of a gen 2 and a v, there is not much difference.
     
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  5. -Jere

    -Jere Junior Member

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    Back from the dead. How do we disable the POS a/c. It sucking gas and power like there is no tomorrow, it runs by itself for NO REASON, even when the light is off it runs in secret. It fogs up the outside window so I have to turn the wipers on when there would be no fog at all with just the fan and fresh air selection.


    Does anyone actually have a fsm with the a/c trouble shooting?
     
  6. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    With my 2010, Canadian purchased Prius, if the AC button is off, it stays off. Push the Off button, then the Auto button, it continues to stay off, and the AC light stays off. Mostly...

    The exceptions:

    1. Set Mode to Heat/Defog, then it might run secretly,, at somewhat lower levels, judging from the ACWatts display on a ScanGauge (with a custom XGauge programmed). The light on the AC button will not go on.

    2. Fairly obvious: if you push the Front Defog button, AC will for sure run, and the light on the AC button will go on. Push the Front Defog button again to turn it off, and the AC will turn off, and the light on the AC button will go off.

    This is on my variant, as describe in the first sentence. I get the sense US and/or later model years (maybe starting in 2012?), the AC tends to come on in more situations? Maybe every dang time Auto is pushed?

    Here's a thought, for Toyota: how about and "On" button, that just turns on the system when it's previously been turned Off, with all the settings as you had them before. Or at the least, an "easter egg" button push, when the system's off, that would do this; say a push of the Fan Speed Up button?
     
  7. -Jere

    -Jere Junior Member

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    You might be on to something with the model years Mendal. Mines a 2013, and no fiddling with buttons (that I've found yet at least ) will keep the a/c off. It's mind boggling to me that Toyota intended the off button to just make the a/c run in secret. It's almost as bad as no way to disable the traction(less) control in snow...

    I'm starting to think I could tape off the humidity sensor to disable it. Anyone know where it may be hidden?
     
  8. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I know where that bugger is, having removed it once to test. Thanks to the way the dash panels go together, you need to remove an inordinate amount of stuff: the shifter, centre console, several central dash panels.

    It's right about where your right knee touches the adjacent dash. It's combined temp and humidity sensor.

    There's a tiny grill at its location.
     
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  9. -Jere

    -Jere Junior Member

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    You've made my day Mendal thanks! I have been thinking about hunting down some of the annoy-a-tron beeping machines behind the dash anyway. If I can take those out and rig an off switch to the secret auto a/c it will absolutely be worth the battle with the dash (y) ;)
     
  10. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I think it'll be frustrating/difficult, to defeat the system's logic, and pulling the dash apart is not a lot of fun. How about hit Auto, the immediately AC off, just make it a sequence. A caution too: you do need to run AC occasionally, say once every couple of weeks, to keep the oil circulating, prevent seals from drying out.

    Here's the vent control system of all but top level Honda Fit, for a drool, lol:

    upload_2019-5-5_7-53-38.png

    You have full control of everything, and all the controls are operable without taking your eyes off the road. I maybe have to join @The Electric Me lol.
     
  11. -Jere

    -Jere Junior Member

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    I can deal with pulling the dash, not looking forward to it but at least there won't be cables everywhere to adjust the vents like most older cars.

    I am thinking the sensor should be a pretty simple thing. Maybe tape will keep the humidity off of it, so it will think it's dry all the time... Or maybe a resistor inline might do the trick instead.

    I'm not worrying about running the a/c for seals or lubrication purposes. Maybe if the seals were natural rubber... But there s been 40 years+ of cars that run a/c one season and they do just fine.

    And as far as the raindance to get the a/c off, I don't use the auto just the fan on 2, windshield and floor, with fresh air. If I change that setting and change it back the a/c light comes on. I click a/c off and it run anyway, I can smell it running and see the accumulator drip tube draining, and frequently watch the outside windshield collect condensation. Toggling a/c light off just makes it run with the light off.

    I see what you mean about the fits controls, automation is not always that intuitive.
     
  12. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Maybe. Still, I've read that "run it periodically to circulate the oil, keep the seals from drying out" adage so many times; it's either got solid mechanic logic behind it, or it's a very well embedded myth.

    Either way, it doesn't hurt. I think too: if you run it once in a while, you'll be more on top of problems, say notice if the cooling performance starts to fall off.

    FWIW, I'm one of the worst offenders, tend to leave it off a long time. But once in a while, when I think of it, I'll run it 5~10 minutes.
     
  13. -Jere

    -Jere Junior Member

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    Yeah you are on to something with myth. The entire system is under pressure, and if the seals go bad it is usually from being unplugged. Natural rubber, engine crankseals once upon a time needed to be gummed up with oil to maintain a seal it's not an issue but that legend still manages to live on some how
     
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  14. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    And don't a/c systems run when you defrost in winter or summer? I haven't worried about an a/c system for at least 40 years of 2 and sometimes 4 simultaneous cars.
     
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  15. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    On my 2010, monitoring ACWatts (X-Gauge with ScanGauge II) the AC compressor would often run surreptitiously, if vent mode was set to Heat/Defog. The AC button light was not lit, and did not light when the compressor was running.
     
  16. Ronald Doles

    Ronald Doles Member

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    I haven't seen the schematics for the Prius heating/cooling system. Does anyone know if this an A.C. unit or a heat pump? If it is a heat pump then it probably uses less power to heat the cabin than electrical strip heaters would. Whether it is just an A.C. compressor or a heat pump, the compressor motor current is a function of temperature. Motor current increases with an increase in temperature and decreases with a drop in temperature. At lower temperatures, motor current may be low enough to be negligible.
     
  17. janshien

    janshien Junior Member

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    Along with the AC light coming on it always defaults to vent instead of recirculate which is very annoying!
     
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