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Outside temperature accuracy

Discussion in 'Model 3' started by funchess, Jun 8, 2018.

  1. funchess

    funchess Member

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    My Model 3 always displays a higher value (+ ~ 5 degrees) from actual outside temperature. For a controlled test, I have measured the temp in my closed garage at 73 F and the car displays 77 F. Outside temps are always higher as well.

    Has anyone else seen this?
     
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    • Informative x 1
  2. Big Dog

    Big Dog Member

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    thanks for posting this. I did a reading today and the display was 5 degrees higher than the actual outside temp (in the shade). But, then I moved the thermo to the bright sun, and it jumped 4 degrees, which was only one degree off of the display reading. Thus, its almost as if the display is showing the temp in the sun as if the thermo is heated by solar radiation. Of course, that is incorrect and why the correct way to read the temp is in the shade.

    Anyone know where the thermometer is located on the M3? Attached to an exterior fender? Yeah, I get that this is a small nit, but still, my 18-year old Saab was excellent in this regard. Never off by more than one degree.
     
  3. Scrith

    Scrith Member

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    Yes, the Model 3 temp generally seems a bit high. My X holds the record though...once I came back to the car after it had been parked outside for a couple of hours and it said it was something like 135 degrees. It was around 90 outside.
     
  4. irishndude4

    irishndude4 Member

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    Yes I have noticed that on the display screen since I took delivery a couple weeks ago. Today it said 105 degrees after being parked outside for a couple hours. It was probably around the low 90s actually. Wish it was more accurate.
     
  5. alseTrick

    alseTrick Active Member

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    My cars have always over estimated temperature by at least 3 degrees.

    Granted, they all are/were relatively old and i didn't own any of them new, do i don't know if the temperature discrepancy increased with age. And none were a Tesla.
     
  6. Whacker

    Whacker New Member

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    I've consistently noticed the same 4 degree discrepancy. My old 5 series was always spot-on once it was in motion. Hopefully the battery thermometers are more accurate...
     
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  7. Thunder7ga

    Thunder7ga Member

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    This seems true in my cases as well, they always seem to run a little high.
     
  8. eCharcoal

    eCharcoal Member

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    I’ve noticed in sunny days, the discrepancy could be more than 10 degrees. We had several days when temperature was around 87 degrees, the screen shows 100. Not sure this is fixable with a software update.
     
  9. chinnam3

    chinnam3 Member

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    Same thing here, it is always higher by 7-8 degrees, but when it was in sun it unusually high. My other 3 cars always showed correct temp (BMW, Honda, and Toyota),
     
    • Informative x 1
  10. peebrayne

    peebrayne Member

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    It's to give the illusion that your car is keeping you much cooler than it really is. Nice try Tesla!
     
  11. Saghost

    Saghost Well-Known Member

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    After parking on a sunny day, this likely isn't an error. The sun heats the parking lot, and the car is slowly baked from the outside in - while greenhouse effects heat the interior.

    If it comes back down during driving, you're seeing real effects of the environment. That doesn't mean the sensor can't also be miscalibrated, though.
     
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  12. Shygar

    Shygar Member

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    I would agree, but it should handle sitting in the sun. Other brand cars don't do this to the extent that I've seen it on the Model 3. Hopefully it can be a software fix but maybe not.
     
  13. Beckler

    Beckler Member

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    If you switch to Celcius that will lower the reading. -Tesla Service
     
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  14. mytez

    mytez New Member

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    Just to add more support....my 3 shows +10 in general. I thought this might be due in some way to my clear bra placement suffocating the sensor but if others are reporting misreadings then it saves me a phone call to the Tesla shop.
     
  15. blackeducator

    blackeducator Member

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    The readings are an average around the car. AND, it is taking in the road/street level temp (which is obviously hotter than anywhere else!). So... if the street temp is 120° and the air temp is 90°, it'll give you an average reading around the car at around 105°. Also, if you are stuck in heavy traffic, the heat generated from other cars close to you will also raise the temp.

    So... just look at it as an average instead of an accurate reading.
     
    • Disagree x 1
  16. chinnam3

    chinnam3 Member

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    #16 chinnam3, Jul 26, 2018
    Last edited: Jul 26, 2018
    Yeah, that is incorrect. It is supposed to show actual outside air temp, not the ground, not the temp of sun and that is what users expect like any other car out there. For that reason placement of sensor is very important, it should not be exposed to sun directly, neither supposed to expose to any parts that might cause incorrect readings. For example Prius temp sensor is mounted at the bottom grill behind bumper, so it is not impacted by sun light, rain etc, It only measures air temp. Not sure where Tesla mounted to cause so much deviation.
     
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  17. Shygar

    Shygar Member

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    Seems like they could probably be more accurate by just reporting the closest weather station to the car, rather than trying to measure it on the car itself.
     
  18. AlexanderAF

    AlexanderAF Member

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    If you're looking for an accurate reading of the temperature outside, pay no attention to your car's thermometer.

    On a warm summer day, it usually displays a temperature significantly higher than the actual temperature, and there are several reasons why. For starters, your car does not actually have a built-in thermometer, but a thermistor.

    Most commonly, the temperature is measured with a mercury thermometer. The liquid mercury inside the thermometer expands and rises to a certain value when heat is added, and contracts and falls to a lower value when heat is removed.

    A thermistor, on the other hand, measures the change in electrical current as a result of heat added or removed. The problem is not with your car's thermistor itself; in fact, thermistors are typically accurate, not to mention small and cheap to make.

    The real problem is where the thermistor is located on your car. Most automakers place the thermistor on the front of the car behind the grille. This location exposes the instrument's readings to re-radiated heat from the road surface.

    If you've ever walked barefoot on the beach or on a blacktop on a sunny day, you likely felt the re-radiated heat directly as your feet burned on the hot surface.

    Car thermistors provide a better representation of nighttime temperatures, when the heating from the sun is lost. They are also more accurate on a cloudy day for the same reason, as well as when traveling at higher speeds and not sitting in standstill traffic.
     
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  19. Saghost

    Saghost Well-Known Member

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    The heat burning your feet isn't being radiated - the asphalt absorbed the sunlight and is really that hot and is burning your feet through conductive heat transfer.

    Similarly, I'd argue that the point you're making is basically the same as mine above - the car is in fact experiencing a higher local temperature than the general in the shade temperature reported on the news.

    Solar heating of the roads combined with extra heat dumped by all the other cars on the road produce air above the roads that's noticeably warmer than the surroundings. On several occasions I've driven in an environment where there's substantial fog everywhere except along the heavily traveled interstate itself.
     
  20. insaneoctane

    insaneoctane Active Member

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    Anybody on this thread actually report their findings to Tesla?
     

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