Heat still coming through vents with heat off.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by mtrel, May 1, 2013.

  1. mtrel

    mtrel Junior Member

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    Recently I noticed that I still have hot air coming through the vents with the climate control system completely off. I can tell that the fan is off because it's not blowing through the vents but the vents are very hot. Has anyone had this problem before or know what it might be?
     
    #1 mtrel, May 1, 2013
  2. bisco

    bisco cookie crumbler

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    welcome! i had the same problem with both my gen II's. the air always felt warmer than outside. i suspect it doesn't shut off all the way, but i never attempted to do anything about it.
     
    #2 bisco, May 1, 2013
  3. mtrel

    mtrel Junior Member

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    Thanks for the response. I didn't realize that was my first post. I've actually been here for a couple of years but I can usually find what I need using the search function.

    I should have said that it's more than a little heat. It's like the heat is on max with no fan running. It's only been in the low 60's here and I think I'll be using the AC to combat it soon. The fan that cools the battery in the back was on the other day and I don't think I've ever heard that running. I'm thinking there must be a valve that lets the hot coolant into the heater core but I'm not sure how to check to see if it's stuck.
     
    #3 mtrel, May 1, 2013
  4. nh7o

    nh7o Off grid since 1980

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    I am not sure if turning the fan off will turn off the rest of the climate control. If the temperature setting is set to "Low" as well, all the way down, and this persists, then yes, perhaps a stuck valve in the heater core loop. Hearing the battery fan running is another issue, and is a concern. How many miles?
     
    #4 nh7o, May 1, 2013
  5. mtrel

    mtrel Junior Member

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    The temperature display is blank. I'll turn it on, turn the temp down and then turn it off again as a test.

    My car is a 2006 and recently passed 100k miles. The temperature in the back of the car could not have been more than 65 or so although it was parked in the sun shortly before. The outside temp was between 60-65.
     
    #5 mtrel, May 1, 2013
  6. bisco

    bisco cookie crumbler

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    perhaps the heat coming into the cabin combined with the warmer daytime temps is causing the battery cooling fan to come on. or the fan could be clogged or the hybrid battery may be overheating. or, you may need a new 12 volt.
     
    #6 bisco, May 1, 2013
  7. nh7o

    nh7o Off grid since 1980

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    The temp control setting says "Low" at the lowest setting, but the cabin temperature display should not be blank.

    The blank display says that perhaps the A/C Amplifier (the computer for the climate control) is not working, such that the cabin air temp info is not being passed through the Gateway ECU to the MFD. The manual says the problem areas for loss of temp control (max heat or max cold only) are:

    1. Steering wheel pad switch circuit
    2. Air mix damper control servo motor circuit
    3. Air mix damper position sensor circuit
    4. Air conditioning amplifier

    I would focus on 4 first. A used one should not be too much $$$.

    And yes to the battery fan cleaning. At 100k, it needs it.
     
    #7 nh7o, May 1, 2013
  8. mtrel

    mtrel Junior Member

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    The temp control setting is what is blank when off. I don't recall having a cabin temp display.

    On my way home today I turned the climate control on, changed the temp from 68 to LOW and then turned it off. Now I have cool air coming through the vents as I drive. I guess even with the system off the valve allowing coolant to the heater core remains open. I expected that turning the system off would mean there would be no heat or AC produced. I guess it's working fine. Thank you all for your help.
     
    #8 mtrel, May 1, 2013
  9. bisco

    bisco cookie crumbler

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    pleasure. all the best.
     
    #9 bisco, May 1, 2013
  10. seckwielen

    seckwielen Member

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    The climate control system will allow air to pass if your air selection is on "outside air" if you place the air selection on "recirculation" then your heat/cool air should turn off completely.
     
    #10 seckwielen, May 1, 2013
    koolingit likes this.
  11. nh7o

    nh7o Off grid since 1980

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    #11 nh7o, May 2, 2013
  12. 2009Prius

    2009Prius A Wimpy DIYer

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    So when you turn the fan off your display doesn't go blank? Mine does.
     
    #12 2009Prius, May 2, 2013
  13. seckwielen

    seckwielen Member

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    So. Did a test. Last night I turned my heat all the way up, set the climate control to fresh air from outside, and turned off the fan. Then turned off the car and went to bed. This morning on my way to work it did exactly what I expected. As I drove the fresh air from outside slowly came inside, hot. I turn the climate control to recirculate an the hot air stopped. Fresh air will always slowly some into the car regardless of the fan. The heater core will always allow a little coolant to pass. See my display below.

    What you are experiencing is perfectly normal.

    ImageUploadedByTapatalk1367502061.982981.jpg
     
    #13 seckwielen, May 2, 2013
  14. nh7o

    nh7o Off grid since 1980

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    OK, that is right. Some confusion on my part, sorry. I was thinking it was the outside air temp display being referred to, which if blank is not right.

    The OP is probably just fine, but I was responding to the comment about the "very hot" coming from the vents. I hope this only occurs after the engine is warmed up, otherwise that heat initially is coming from the PTC electric heater element which reduces mpg when used, and should not be on if you don't want it. Hopefully the system is smart enough to not do that.
     
    #14 nh7o, May 2, 2013
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