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Outside Temperature Reading

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by jburns7654, Oct 23, 2013.

  1. jburns7654

    jburns7654 New Member

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    So, this may sound strange but from the get-go of owning my Prius I have always sort of doubted the accuracy of the outside temperature reading. I am not totally worried about that part, as I don't really care about the reading, but I would love to understand something. When the thermometer reads the temperature as "37 degrees" it displays this bar that states it as such. The same bar where it notifies you if you change the temperature or volume via the steering wheel. So, I guess my question is , is there something specific about that number or is it just a quirk of my individual Prius? Also, it is worth noting that no other temperature causes it to display this message, only 37 degrees.
     
    #1 jburns7654, Oct 23, 2013
  2. wjtracy

    wjtracy Senior Member

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    Where are you located? Is that degrees F or C?
    We find the reading to be fairly accurate for outside temp.
    Seem to recall some significance of the temp, possibly warns of black ice IIRC?
     
    #2 wjtracy, Oct 23, 2013
  3. jburns7654

    jburns7654 New Member

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    I am in southeastern Wisconsin so Fahrenheit.


    iPhone ? - now Free
     
    #3 jburns7654, Oct 23, 2013
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. I've noticed that the outside temperature reading tends to display in increments of 2 degrees F. I think that the internal logic computes temperature in whole C degrees, but then the display has to convert the temp to F which results in some rounding since an F degree is 1.8 x C degree (plus 32).

    2. The purpose of the warning when the temperature is 37 degrees F is to point out that the outside temp is close to freezing, hence you should be cautious as the roads may be icy. 2004 and 2005 Prius have a warning light that appears continually when the temp is around that level or lower. That light was eliminated in later model years in favor of a brief warning displayed on the MFD.
     
    #4 Patrick Wong, Oct 23, 2013
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  5. uart

    uart Senior Member

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    That's curious. I've never noticed it, but then again it's mostly over 40F here all winter. I'm pretty certain (assuming degrees F) that's the same temperature at which the snowflake icon appears on the dash to warn you of possible icy roads. So I guess that's the connection.
     
    #5 uart, Oct 23, 2013
  6. wjtracy

    wjtracy Senior Member

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    ...couple of Wikipedia explanations for why air at 37F (vs. 32F) may be selected as a warning point. Gee I don't think my 2006 has the snowflake...

     
    #6 wjtracy, Oct 23, 2013
  7. nerfer

    nerfer A young senior member

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    My 2006 does have a snowflake when the temperature starts at or drops to 37'F. But the outside temperature reading is always on the top bar of the MFD (in the consumption bar screen anyway), except when it's temporarily replaced by changing the radio station or adjusting the desired internal temp.

    The temperature reading is generally a bit warm (because of radiated heat from the sitting engine) until you drive about a mile or so.

    The temperature does generally jump by 2'F, but occasionally 1'F. As pointed out earlier, F=9/5C + 32, or 1.8*C + 32. So at 4 readings out of 5, there's a 2' step between conversions, and once out of 5 it's a 1'F step. For our metric minded friends, they always see 1' C increments.
     
    #7 nerfer, Nov 10, 2013
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