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AC is ON even when selected to OFF?

Discussion in 'Model S: User Interface' started by AndreyATC, Aug 23, 2014.

  1. AndreyATC

    AndreyATC Member

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    Hello all
    Temperatures have been on a low side for a while
    I usually turn on a fan to circulate air
    however I noticed that when the fan is on the AC kicks in as well
    no matter what I do I cannot turn it off
    I can understand if this was an auto setting but this is a manual override when I turn it off
    example:
    outdoor temp 64f, car setting 72f, cabin temp is 75f
     
  2. scaesare

    scaesare Active Member

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    It seems to do this for dehumidification purposes more than I'd like as well...
     
  3. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I contacted Tesla about this. The car monitors relative humidity and will activate the compressor when the humidity gets too high to prevent window fogging, even when the setting is "A/C off". I was told this is intended behavior.
     
  4. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Other cars do this same thing. Normal and expected.
     
  5. Electric700

    Electric700 Member

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    Also if the battery requests cooling for optimal efficiency, the compressor will turn on. As a result, my guess is that you may experience a cooling benefit even with just the fan on.

    Still, most of that cooling is going toward the battery. Other cars like the Chevrolet Volt (which has a battery cooling/heating system also) work this way too.

    Consider using the heated seats or increasing the cabin temperature if you're too cold.
     
  6. scaesare

    scaesare Active Member

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    My issue is that often I'd like to have outside temperature fresh air thru the vents... particularly in the spring and fall. Even when there's not sufficient humidity to come even close to fogging the windows, it will enable the A/C. And if the window-vents are enabled, the compressor remains on the entire time.
     
  7. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    #7 andrewket, Aug 23, 2014
    Last edited: Aug 23, 2014
    This was true for the roadster but I don't believe true for the S. The S has independent cabin and battery cooling systems.
     
  8. scaesare

    scaesare Active Member

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    Sort of. The A/C subsystem is common to both, but can selectively loop the battery and cabin in or out of the chain.
     
  9. Electric700

    Electric700 Member

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    Ah, very interesting. Good to know.

     
  10. scaesare

    scaesare Active Member

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    As a result, I expect there are some situations where demand on one side of the loop can cause fluctuations on the other... some of that could factor in.

    Here's a thread I started about this a while back that has a good opening picture that illustrates the system: Overall Thermal Management
     
  11. theapple

    theapple Member

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    I've noticed the same, but I was under the impression it only happened when the AC kicked on to cool the battery; I can feel it cycle on and off, usually because it gets unpleasantly cold, but it behaves most of the time.

    Far, far worse in my opinion is that the 'recirculate' setting also has a mind of its own. It likes to switch to fresh air while you're following a diseasel truck, and also in the winter, when doing so causes it to gobble up precious battery capacity to heat the -10 degree outside air instead of the 70 degree cabin air. This is my only real gripe with the car, but it definitely annoys the heck out of me.
     
  12. AndreyATC

    AndreyATC Member

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    +1
    i'd like to be in control of the whole system
    it doesn't make sense when the car decides when to turn on the AC compressor
    if it gets foggy I can just press the button, what's the big deal?
    I actually don't remember having this "future" with previous firmware
     
  13. mknox

    mknox Well-Known Member

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    I have not seen this behavior, and it gets pretty stinkin' humid around here. In my case, the a/c compressor will only kick in (if set to off) if I select defrost mode either alone or in combination with another vent setting.
     
  14. scaesare

    scaesare Active Member

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    Assuming by "defrost" you mean specifically enabling the separate button on the main lower button bar (not the popup panel). If so, try this:

    Set the A/C to off, and then enable all the vents. Set the temp to "Lo" (so that there's not potential for the heater to kick in).

    Observe the air coming out the vents is colder than outside ambient.
     
  15. Lloyd

    Lloyd Active Member

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    I believe that if the temperature of the battery is above the active cooling target, the AC will kick on, and some of the cooling will be ducted to the cabin if the temperature inside calls for cooling. Not verified, just MO.
     
  16. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    This is the response I received:

     
  17. mknox

    mknox Well-Known Member

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    Yeah, either hitting the discrete Defrost button OR selecting defrost on the pop-up panel would result in the compressor kicking in. When you say "enable all the vents" I assume that would include the defroster vent, and as I say, it WILL kick in if the defroster vent is selected.

    Have you seen the a/c kick in if the defrost vent is NOT selected? By that I mean either floor or dash or both floor/dash vents. I have not personally seen that happen.

    Having the a/c compressor kick in whenever the defrost vent is selected is consistent with other vehicles I've owned in the past, but having it kick in when only the other vents are selected, and a/c is switched off, is not.
     
  18. scaesare

    scaesare Active Member

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    I have other vehicles where if the A/C was disabled, i could get fresh air from the windshield vents without the A/C kicking in.

    My preference would be for the the "defrost" main panel button to be a "quick preset" that enables windshield vents, turns on A/C, selects appropriate recirc settings, etc...

    However when I manually over-ride settings on the sub-panel, I'd like the car to honor that.
     
  19. mknox

    mknox Well-Known Member

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    I agree, and come to think of it, even on my past cars that did turn on the compressor in defrost mode, I could hit the a/c button and turn it right back off again. (I wonder if that works with the Tesla... it would be at least a workaround to using the defrost vent without the a/c running)
     
  20. scaesare

    scaesare Active Member

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    Interesting idea worth testing...
     

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