Hot air coming out all the time when gas engine is on

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by thorn, Mar 22, 2020.

  1. thorn

    thorn Junior Member

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    I just drove my 2017 Prime mostly on the highway and the heat was blasting out even with the fan turned off. Only when I went to electric did it cool down. I don't have access to the service manuals and it's still under warranty but I don't want to drop it off at the dealer do to the COVID-19 and they may close down soon. I guess it could be a sticky heater control valve, a control signal that's always on or faulty thermostat. I did find a general schematic on the heating system and there is a heater radiator unit that brings heat from the engine. I looked around under the hood and see some hoses coming and going through the fire wall.

    Has anyone else experienced this before?

    Thanks!

    How does the heat pump work in a Toyota Prius Prime plug-in hybrid?
     
  2. bisco

    bisco cookie crumbler

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    you don't say what your hvac settings are
     
  3. thorn

    thorn Junior Member

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    Started out with the fan was on, auto off, no AC. I turned the fan off and heat still comes out when moving along until I went to electric.
     
  4. bisco

    bisco cookie crumbler

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    temp set to...
     
  5. dig4dirt

    dig4dirt MoonGlow

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    recirc or fresh air?

    Over the winter I use recirc to keep the cold air out,
    but I have noticed with fresh air now, the heat from engine is coming in now.

    Diff model i know, but outside temps are changing?
     
  6. FuelMiser

    FuelMiser Senior Member

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    That's normal! The car will let fresh air pass through the HVAC vents using the last temperature set when you turned off the system. It will warm the outside air based on the temp setting with you turned it off. If you want to turn off the HVAC, first lower the temp all the way down and then you will get fresh air without any added heat. You can also manually select the vent settings with the system off.
     
  7. thorn

    thorn Junior Member

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    I lowered temp to LO and it was still coming out very hot. I tried higher fan setting and then no fan and then it was really hot as the air still flows through as you are moving but not as much. It was 51F and sunny so no heat was really needed. Recirc was open. Once I went to all electric the air coming out cooled down fast. If I get a chance I'll try it again. Not much reason to drive anywhere now.
     
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  8. bisco

    bisco cookie crumbler

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    hmm, does sound a little odd. i do notice the air through the engine compartment can be warmer than outside temp, but how warm is warm?
     
  9. thorn

    thorn Junior Member

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    It was hot enough that I could not keep my hand on the vent and I started smell some strong plastic smell, that's when I turned on the fan so at least it could dissipate the heat from the core which helped. I had to open the window since it was getting too hot in the car! I was heading home and once I was in range to switch to elec I did. The air coming out cooled off in a few mins. I would guess no coolant was flowing through the core from the engine since it was off.
     
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  10. bisco

    bisco cookie crumbler

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    might be worth a 12v reboot
     
  11. WilDavis

    WilDavis Senior Member

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    Lots of hot-air? Sounds like it's suffering from the "Washington Syndrome".


    Posted via the PriusChat mobile app.
     
  12. thorn

    thorn Junior Member

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    Do you pull the + connector on the 12v battery and wait a few mins.? It's not hard on the computer?
     
  13. bisco

    bisco cookie crumbler

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    negative. won't hurt anything, but you can lose radio presets, window function, trip meters, etc.
     
  14. fotomoto

    fotomoto Senior Member

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    I had the same thing happen on a previous C-Max except it only occurred on the passenger side vents. :confused:

    Next time it happens (don't turn off), take it straight to a dealer so they can verify for easier warranty process. I had no codes or trouble lights.
     
  15. thorn

    thorn Junior Member

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    What caused it?
     
  16. fotomoto

    fotomoto Senior Member

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    HVAC controller part of some sort. I assume it was part of the hardware to allow dual (passenger) control. Having the service manager see it happened really helped speed up the repair process.

    GOOD LUCK!
     
  17. thorn

    thorn Junior Member

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  18. thorn

    thorn Junior Member

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    I dropped it off at the dealer and he said they found a stuck/bad solenoid for the right hand side and ordered the part. He thinks that might be it but they will see. The high side pressure is low, 98 vs 150 but it could be because of the right side problem.
     
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