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heating blows cold air

Discussion in 'Gen 3 Prius Main Forum' started by memento84, Oct 28, 2017.

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  1. memento84

    memento84 Junior Member

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    just noticed couple days ago, became apparent at 37F. air that comes out is cold, maybe little warmer than ambient. blower works ok. any ideas ? relay/fuse ???
     
    #1 memento84, Oct 28, 2017
  2. BZzap!

    BZzap! Senior Member

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    Check your temperature setting ?
     
    #2 BZzap!, Oct 28, 2017
  3. memento84

    memento84 Junior Member

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    i have set it at HI , but also tried all settings 70-85F. so that is not it. any other ideas ?
     
    #3 memento84, Oct 28, 2017
  4. David Beale

    David Beale Senior Member

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    Was the coolant changed recently? There may be an air bubble in the system. It's also possible the electric coolant pump has failed.
    I see you have a 2007 Prius, which is a GII. Unless you haven't updated your info. ;)
     
    #4 David Beale, Oct 28, 2017
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  5. bisco

    bisco cookie crumbler

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    thermostat, blocked heater core.
     
    #5 bisco, Oct 28, 2017
  6. memento84

    memento84 Junior Member

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    changed water pump couple months back. heating was fine.
    blocked heater core - how to troubleshoot that ?
     
    #6 memento84, Oct 28, 2017
  7. bisco

    bisco cookie crumbler

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    waterpump is not the thermostat, is it? maybe need to read the coolant temp. not sure how to check the heater core.
     
    #7 bisco, Oct 28, 2017
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  8. memento84

    memento84 Junior Member

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    1 clue - I could hear some gurgling noise, seemed like it was somewhere under the dash, but no leak ever (thought that was coming from engine compartment) - would that mean some obstruction in the heater core ??????
     
    #8 memento84, Oct 28, 2017
  9. bisco

    bisco cookie crumbler

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    gurgling might mean you need to bleed the system, but i'm not positive.
     
    #9 bisco, Oct 28, 2017
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  10. Raytheeagle

    Raytheeagle Senior Member

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    If a Gen3: Have you checked the hoses and coolant in the overflow and they are warm?

    If a Gen2: have you checked the level in the radiator and are the hoses warm?
     
    #10 Raytheeagle, Oct 28, 2017
  11. memento84

    memento84 Junior Member

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    I will try to locate hoses for the heater core - it seems like a common problem (kind of), will try to blow it thru, opposite direction that it normally flows.
     
    #11 memento84, Oct 28, 2017
  12. memento84

    memento84 Junior Member

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    it is 3rd Gen.
    Coolant in overflow should be warm right ? the return one (upper) should be warm/hot right ?
     
    #12 memento84, Oct 28, 2017
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  13. Raytheeagle

    Raytheeagle Senior Member

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    The overflow and hoses should be hot if the full warm up cycle has been completed;).
     
    #13 Raytheeagle, Oct 28, 2017
  14. memento84

    memento84 Junior Member

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    I checked that when replaced the water pump, and they were ok - will do it again! how hard is it to locate heater core hoses ?
     
    #14 memento84, Oct 28, 2017
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  15. Raytheeagle

    Raytheeagle Senior Member

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    Water pump was replaced? How many miles? What was the cause of the previous pump failure?

    The easiest hose to check is the one off of the overflow reservoir ;).

    Keep us posted (y).
     
    #15 Raytheeagle, Oct 28, 2017
  16. memento84

    memento84 Junior Member

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    186k, pump died. so the return to overflow is heater core "out" ? will update asap
     
    #16 memento84, Oct 28, 2017
  17. Raytheeagle

    Raytheeagle Senior Member

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    The electric water pump died:(?

    Did you hange it yourself ? Get it back if not or ask what the failure was from?

    Here are 2 pics of water lines to check:

    Off of the overflow reservoir 57451CF1-B5CF-4947-A0FE-26324C588AED.jpeg

    On of the egr cooler 50759C31-DA84-410C-9A83-5F3794DDB7E2.jpeg

    Keep us posted(y).
     
    #17 Raytheeagle, Oct 28, 2017
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  18. BZzap!

    BZzap! Senior Member

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    Does the blower work?
    After all that’s said an done, it sorta points to a bad Blend door actuator. Almost all modern cars have the coolant circulatiing through the heater core constantly. The heat is controlled by opening and closing these doors with a motor that is controlled from the HVAC module. It’s all electronic. It’s also possible that the control head is malfunctioning.
     
    #18 BZzap!, Oct 28, 2017
  19. BZzap!

    BZzap! Senior Member

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    BTW the coolant control valve is electronically controlled... no vacuum involved. This might be the source of your problem. You might want to turn the heater on and try gently tapping the control valve then check to see if you get heat. Another scenario is no signal from the controls. Fuse, maybe? Bad control module? Bad valve?
     
    #19 BZzap!, Oct 29, 2017
  20. David Beale

    David Beale Senior Member

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    I'm still thinking he's got an air bubble in the heater lines, after replacing the water pump. Simple things first! ;)
     
    #20 David Beale, Oct 29, 2017
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