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Temperature reading wrong.

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by tigerpilot, Jul 19, 2016.

  1. tigerpilot

    tigerpilot Member

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    On our new 2016 the outside temp display is always three or four degrees warmer than the actual outside temp.
    It doesn't seem to change regardless of the length of the drive.
    The service writer told my wife that it's because the sensor (thermocouple) is encased in a steel jacket.
    I don't care if it is mounted in a 12" block of steel. It should be correct.
    Our 2015 and 2009 both read correctly. Does anyone know if this is computer adjustment or a thermocouple replacement situation?
    Thanks, Don
     
  2. bisco

    bisco cookie crumbler

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    what do you use to compare it to? mine generally reads 2 degrees lower than my home outside thermo. but i have no idea if that is correct.
     
  3. tigerpilot

    tigerpilot Member

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    I use a calibrated Thermopen. It's the same device I used with the other two Prisus. A 2009 and a 2015.
    It's accurate within a 1/2 degreee.
     
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  4. bisco

    bisco cookie crumbler

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    nice. how far off are the other two?
     
  5. tigerpilot

    tigerpilot Member

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    Both other cars are within one degree.
     
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  6. bisco

    bisco cookie crumbler

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    idk where you go from here, call toyota, demand satisfaction?
     
  7. ssdesigner

    ssdesigner Active Member

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    Mine is the same. 2016 Prius 2. Always reads between 80-85 whether I'm out in 90 degree weather or parked in my cool, underground parking garage.
     
  8. bisco

    bisco cookie crumbler

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    that's not the same, that's worse!:p
     
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  9. ssdesigner

    ssdesigner Active Member

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    lol, right?! I know for a fact that it's between 65-70 in my parking garage, and my car reads low 80's every time I get in.

    Weird.
     
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  10. dorunron

    dorunron Senior Member

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    I think it is due to the location of the sensor. Ours is in front of the evaporator (I think that is the term). Tends to read hotter than actual temp. Actually saw 107 degrees a few days ago. It was really only 99. Car was also parked outside in direct sunlight on a asphalt parking lot. I have seen the temp read higher on the super slap with rush hour traffic and then drop when i pull off to the side of the highway.

    As with all things manmade, far from perfect.
     
  11. RRxing

    RRxing Senior Member

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    Ambient temp sensor is (dealer?) adjustable on the Gen III to + or - 2 degrees. Don't know about the Gen IV.
     
  12. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    It's maybe using these temperature readings to make decisions regarding warm up behaviour and what not?

    Anything mod'd, say a front bra?, that would be insulating the temp sensor, picking up engine heat, just a guess.
     
  13. Coast Cruiser

    Coast Cruiser Senior Member

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    I wish my car had an accurate inside temp gauge. I know when it's blazing outside... just by sticking my ugly mug out the window. :LOL:

    I'm more concerned about the inside. When I set my AC at 65? Baloney!! My Prius never cools down to 65. I'm gonna get a little thermometer and stick in there somewhere.
     
  14. WilDavis

    WilDavis Senior Member

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    Sorry, I must be missing something here! It's a bloody car, fer Christ's sake! …if it's that important to you, have your dealer fit a calibrated Thermopen (or two, better have one at the front and one in back - to get the average outside temperature) and while they're about it how about a hygrometer and a rain-gauge, and a variometer… and a partridge (in a pear-tree) :eek: - me? I just looks at the temp gauge, and if it seems wrong, I just sticks me big toe out the window! :confused: ;):) - I don't think this will help - Wil (…sorry, do I look as if I care?)
     
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  15. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    ^ This kinda reminds me of the concern over speedometer inaccuracy. If the speed limit's 50, that's the most I do. I don't stress that I'm actually going 48~49.

    Still, with the ambient temp gauge, maybe the car is using that info to make warm-up decisions.?
     
  16. jbkendrick

    jbkendrick Active Member

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    Is the temperature reading supposed to be correct when you first get in the vehicle. Most of my other recent vehicles need to be driven for a bit for the temperature to be accurate. I'll have to check if my Prius is like this, but the other cars have generally displayed the temperature of the car when I shut down the last time. J
     
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  17. ssdesigner

    ssdesigner Active Member

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    Then why have a number on there if it's not to work? Mine may as well read threve.
     
  18. ChapmanF

    ChapmanF Senior Member

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    The sensor's behind the front bumper cover, right where a lot of hot air from the engine compartment and cooling system will be whenever isn't moving fast enough to force it out with fresh. It should read about right before a cold start after sitting all night, but is likely to read high if the car was just parked for a shorter time, then come down closer to reality as the car is driven.

    If you compare it to a Thermopen, you should probably compare with the Thermopen in the same location behind the bumper cover. If you then do find a systematic error that's within a couple degrees either way, there is probably a correction setting that can be made in Techstream if you care that much; there definitely is such a setting for Gen 3.

    -Chap
     
  19. kithmo

    kithmo Couch Potato

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    I bought small digital thermometer years ago that I sometimes put in the car, it only reads up to 42C (108F) then goes blank above that and it gets way hotter than 42C when parked in the summer sun, so I don't know how hot it actually gets over 42C. It's suprising how hot it gets in the winter sun too.
     
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  20. RRxing

    RRxing Senior Member

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    I keep an analog thermometer in the center vent to monitor climate control system temps (particularly the AC). On 90F (32C) days I've seen the interior temp north of 160F (71C). If it's not forecast to rain, I keep the windows cracked open on hot days.