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WARNING: Dangerous new/changed functionality

Discussion in 'Model S' started by whitex, Oct 9, 2016.

  1. whitex

    whitex Member

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    Just wanted to share a dangerous encounter with new v8 feature. I upgraded to 8.0 about a week before going on a 2600 mile trip. While driving at night, in humid conditions I started to get condensation on the outside of the windshield. Wipers would take if off but I figured I could just heat up the glass to reduce the need for wipers to keep wiping, so I turned on the front windshield defroster (tap twice so the icon turned red) - within a fairly short time my windshield was fully covered by condensation and wipers now smudge it rather than wipe it. So here I am, driving 55mph through a winding rural highway, with almost no front visibility and a big rig bearing down on me from being. It turns out in v8 red HI defrost now means high AC, not high temp as it used to. Either some genius PM driving in dry California weather decided HI defrost works best with max AC, or Tesla is not QA'ing basic functionality, potentially causing dangerous driving situations. What's next, the little triangle for hazard light will change functionality to drag race launch mode? WTF Tesla? Can we at least get an option to never upgrade so I can avoid such "improvements" that could kill me?
     
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  2. kirkbauer

    kirkbauer Member

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    Ideal defrosting is max heat plus max A/C. Cooling and the heating the air makes it less humid.
     
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  3. Saghost

    Saghost Active Member

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    I feel like I'm missing something. How do you believe that the air conditioner hurt in this situation?
     
  4. Electric700

    Electric700 Member

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    I have had condensation problems at night too, but I just set the temperature at or above 78 F and activate the front windshield vent setting. If it gets bad while driving, turn your emergency lights on and try very carefully to pull over until the condensation clears.
     
  5. amallah

    amallah Member

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    I didn't even know about long pressing defrost. I do know that hot air holds more moisture than cold air (it's a better sponge). Also, air conditioners dehumidify air in the process of producing cold air. So, to me, it's an improvement to the options to be able to control BOTH the temperature AND the dehumidification effect, so you can use both together to more quickly defog the car:

    I saw this video last winter and it really helped explain things:
     
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  6. ggr

    ggr Roadster R80 537, SigS P85 29

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    There's a big difference between condensation on the inside and condensation on the outside. For inside, you want A/C to dry the air (and if you can re-heat it at the same time, that's even better). For outside you want heat to make the glass warmer than the air, at which point condensation will stop.
     
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  7. ICUDoc

    ICUDoc Member

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    A/C won't help condensation on the OUTSIDE, guys (which is what the OP was trying to treat).
    (Soz, GGR beat me to it...)
     
  8. trils0n

    trils0n 2013 P85

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    The double-tap for red HI defroster has always done HI temp and max AC. Does it no longer perform that way?
     
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  9. whitex

    whitex Member

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    It made the windshield colder causing a lot more condensation, more than the wipers were able to deal with.
     
  10. whitex

    whitex Member

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    Nope, now it just blows freezing cold air. It really should be showing "Lo" rather than "HI", and icon should not be red.
     
  11. Saghost

    Saghost Active Member

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    Wow. That's some powerful AC. Ice never seen a windshield so cold it condenses faster than wipers can clear away, let alone one that gets that way instantly. It usually takes a few seconds to even cool off the coils, let alone the air and the windshield.

    What I have frequently seen is condensation on the inside immediately after turning the defroster on, until the AC dries the air enough to stop it.
     
  12. whitex

    whitex Member

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    #12 whitex, Oct 9, 2016
    Last edited: Oct 9, 2016
    I never said instantly, it took 30-60s (not sure as I was kind of busy trying to not crash), the problem is as you get more condensation you keep thinking heating the windshield is what you need, so you won't turn it off (think what would happen if brake pedal was accelerating, the driver would instictively keep pressing the brake even harder). It gets to a point when the windshield is cold enough that the new condensation shows up immediately after the wiper has passed, leaving the wipers going full speed but only glimpses of the road. Night darkness and lights shining on the windshield amplify the danger.

    Anyhow, we could argue what is better for defrost, however my point is that changing the behavior like this creates a potentially dangerous situations. If the car came with accelerator and brake reversed, people would complain but know about it. If the reverse happened via an over the air update, that would likely cause accidents.
     
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  13. FloridaGary

    FloridaGary Member

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    Great video that explains the best way to remove condensation. I have always done it this way, but never realized it was the best way.
     
  14. whitex

    whitex Member

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    This video talks about inside condensation, my situation was outside condensation (cold window, humidity outside condensing on a window).
     
  15. Cosmacelf

    Cosmacelf Active Member

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    What does the manual say should happen?
     
  16. JPUConn

    JPUConn Member

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    My windshield started to fog this am (first time for me in the Tesla) and I had success with the two press until the defrost was red. mine read HI and I thought the temp was warm coming out but didn't pay that much attention.

    Was just under 50 degrees this am and the car was comfortable with defrost running and windows closed.
     
  17. boonedocks

    boonedocks Member

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    To the OP I know exactly what you are talkng about. I have had this happen late at night with temperatures in the 65-75 range. I think that the problem is that when it is that cool, high humidity outside, and the A/C on that there is air coming from the top window vents that cools the window too much. I wish that the setting for dash vents ONLY put air it is those vents.
     

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