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Does the heating require A/C on?

Discussion in 'Model X' started by tslaEbay, May 31, 2017.

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  1. tslaEbay

    tslaEbay Member

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    Hi Folks...yesterday the outside temp was 60 and I bumped up the cabin temp to 70 while keeping the A/C off.
    I did not get hot air. Is this supposed to work like this?
     
  2. Algbc

    Algbc Member

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    i have the same question!
     
  3. David99

    David99 Active Member

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    The AC compressor and the heating element are separate and logically the AC would not be needed to heat the air. I did notice that Tesla will run the AC a little when driving in the rain even when the outside temp is lower. The AC dries up the air which helps prevent fogging of the windows. I used to do that manually in my old cars which worked great.

    Maybe, and I'm really just guessing, the switch that used to only turn off the AC compressor, now disables both the AC compressor and the heating element.
     
  4. JOEV1

    JOEV1 *****joe

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    #4 JOEV1, Jun 1, 2017
    Last edited: Jun 1, 2017
    Its called reheat. To some of us it sounds paradox to turn-on heating and cooling (AC) simultanously. In older models one had to switch-on both indivitually. As in newer models it is done by just one button..
    The way it works is pure phyics as we learnd it back in school: evaporation and condensation or change of state of H2O.

    We all experienced a foggy wind screen at some stage and used paper tissues to wiped for a clear view.
    Well, let physics do that for You: By turning-on the heater, the air in the car will pick up and hold more moisture (humidity) and by turning on the A/C the humit and warm air condenes on the cool evaporator and the moisture drips-off. In no time the air inside the car is dry.
    Now be sure the water discharge valve (one-way valve) works and the water can leave. Thats one of the service points that AC companies must not forget. Otherwise one ends up with a flooded car. (flooded from inside or outside)
    And... do not run an AC without filters... or You have a real mess.


    )
     
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  5. tslaEbay

    tslaEbay Member

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    @David99, @JOEV1...thanks for the reply....coming from ICE car this was bit confusing.
    You are saying..single button controls both the heat and A/C in Tesla?
    There is no free heat in Electric car as compared to ICE car.
    So..it is better to leave the A/C on always and just adjust the cabin temp?
    Tesla manual recommends using auto mode always and adjust the temp. But..sometimes...I don't like
    the fan blowing crazily. Then I adjust the fan speed and it gets out of auto mode.
     
  6. David99

    David99 Active Member

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    Yes it's best to let the car do all the climate control. Just adjust the temperature up or down depending on if you want it warmer or cooler. I wish Tesla would do away with the temperature numbers altogether because it is just confusing. We think a certain number is comfortable but nothing could be further from the truth. Humidity makes a lot of difference as does air motion (wind or lack of). Te exact same temperature of dry air blowing at you feels much cooler than no air motion and high humidity.

    Tesla knows all that and intelligently adjusts airflow and AC (to dry the air) and heater and it even knows the sunlight intensity and angle and adds that into the calculation! So what I learned to do is leave it on auto and then adjust the temp up or down depending on how I feel. I completely ignore the numbers. That works best IMHO.
     
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  7. Xenius

    Xenius Member

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    Consider that "AC On" as "Air Conditioning (hot or cold)". If that setting is off you'lre only at most circulating whatever air you have (or taking more outside air in, etc).

    I also found this odd at first, but like others have said unless I specifically am putting the windows down or opening the pano roof, I leave climate control on and adjust it up or down as I feel.
     
  8. JOEV1

    JOEV1 *****joe

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    Spot-on! DAVID99, let the car do the climatic control. Its sensors and hardware knows best. what to do.
    However, it never hurts to open doors and windows when the car was sitting in the sun for hours.
    But after, on the road, one should let the system do the job... meaning that one should not interfere by opening a window to "help" the AC system.
     
  9. AzEd

    AzEd Member

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    In the Spring and Fall, the temperatures in Phoenix can range from 60F - 85F in one day. During the heat of the day, I set the temperature control around 72F - 75F and the A/C is on as expected. When I get in the car the next morning, the outside temperature could be 65F - 70F and the heat comes on, which I don't want. I want outside air until it gets too hot (75F - 80F). As a rule, when I park the car for the night, I turn the A/C off to get cool outside air the next morning. I have to leave the climate control on without A/C to use the fan for outside air. In the winter (below 60F) I have to set the temperature to "LO" to keep the heater from coming on and still have the fan on for outside air. The temperature control only goes from 60F - 81F and sometimes I'm comfortable below or above those temperatures with only outside air. Letting the car do climate control automatically does not work for me.
     
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  10. tslaEbay

    tslaEbay Member

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    @AzEd...you explained my problem well. Thank you.
    I wish they had a way to control A/C on/off from the steering wheel.
    Sometimes..I say to myself just leave it in auto mode always but for the reasons you mentioned
    I end up manually adjusting the controls all the time. I don't want to burn the battery on unnecessary heating.
    It is distracting while diving to control the A/C from the center screen.
     
  11. David99

    David99 Active Member

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    I live in a very similar climate and spend a lot of time in Phoenix so I know the climate there well. Yes deserts climate means it can get cold over night and then very hot during the day plus the direct sunlight. So yes sometimes in the morning the car and cabin is cold and for a minute the heater will kick in but that's literally just a minute. I mean what would you expect? Both the car and the cabin are colder than what you tell the climate control to be at, so of course the heater will come on. That's literally what you ask the car to do.

    Hm I think what you want is a mode where the climate control is completely disabled and you just control airflow. I know several people that like to do things that way, at least in some situations. In this mode, the temperature buttons would change to adjust the far speed only. To be honest that's what I wanted to do as well when I had my car new, mostly to conserve energy. Now I just use the climate control the way it's designed and let the car do it's thing. The energy consumption by the climate control in our kind of climate is really minimal.

    One reason why I like the automatic behavior so much here in Los Angeles is the ocean. Both the temperature and humidity changes drastically depending how far or close you are to the ocean. I love how the car keeps me comfortable while I drive from a 90 degree heat to a 65 degree gloomy, moist beach town.
     

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