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scangauge mystery - temp rising with engine off

Discussion in '3rd Gen Tundras (2014-2021)' started by TTund16, Feb 24, 2020.

  1. Feb 24, 2020 at 4:46 PM
    #1
    TTund16

    TTund16 [OP] New Member

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    I have a scangauge and if I leave the key in the ignition on position (engine is off), my intake temp and trans temps (Pan and torque converter) slowly move higher and higher.

    I was playing with the computer setup and left the key in the ignition on position for several minutes and noticed the temperatures kept rising. Initial temp reading were all correct since the car was not driven for a few days and all temperatures matched the outside temp …

    asked a co-worker who has ultra gauge to try it and he saw the same thing! so its not a scangauge issue.

    curious what's causing this?
     
  2. Feb 24, 2020 at 5:59 PM
    #2
    Johnsonman

    Johnsonman New Member

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    Heat rise. It occurs in all internal combustion autos with a radiator (+trans). It is very normal to rise 20+ degrees in engine coolant, then of course it slowly drops or quickly if fired back up.
     
  3. Feb 24, 2020 at 5:59 PM
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    Neutron

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    Without coolant circulation the heat transfer from the solid components will cause the fluid temp to rise. Its normal. Engines do the same thing. If you have a vehicle with an electric radiator fan, after you shut the engine off and leave the key on the fan will usually kick on after a short time
     
  4. Feb 24, 2020 at 6:49 PM
    #4
    TTund16

    TTund16 [OP] New Member

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    are you guys talking about the heat rise in the transducers (due to current) itself with the engine being off?
     
  5. Feb 24, 2020 at 7:14 PM
    #5
    Neutron

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    S&B intake, Corsa exhaust, TRD rear sway bar, Spec-D tail lights, wireless center console charger.
  6. Feb 24, 2020 at 7:30 PM
    #6
    14burrito

    14burrito IG @14burrito

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    OPs car was cold, off for an extended period of time so this isn't a heat transfer "issue", instance or occurrence.
     
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  7. Feb 24, 2020 at 7:36 PM
    #7
    Neutron

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    I didn't see that detail, sorry.
    Cant see how a temp can rise from ambient temperature without the engine ever running.
    Very strange
     
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  8. Feb 24, 2020 at 11:28 PM
    #8
    TTund16

    TTund16 [OP] New Member

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    I should have been more clear ... As @14burrito mentioned, car was sitting for 3 or 4 days and I turned the key to ignition on position (engine off) to read the scangauge intake temp, trans oil pan temp and trans oil torque converter temp. All scangauge temperatures matched the outside temp displayed by the car and also matched the outside thermometer I have in the yard. I was pretty impressed with the scangauge readings ... I then started to play with computer & navigation setup (engine still off) and noticed the scangauge temps slowly started to rise and after a while they went up as much as 10-15°F higher ... When I started the engine, all temperature readings immediately dropped back to initial readings and started to slowly rise as expected since the car was warming up.
    I have tried this test couple other times with the same result.

    Asked my co-worker to try it with his ultragauge and he saw the same thing.

    That's why I thought maybe the current thru the transducer is causing this. Maybe the current is dropping since I left the ignition on and the battery was also not in the best of shape.
     

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