No heat in 2010...not sure of next step

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Norwich2, Nov 10, 2018.

  1. Norwich2

    Norwich2 Junior Member

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    Well, I have a used 2010 I bought in May 2018 and only now is it cold enough (40degF) to need the heater, but I barely get any warm air...just less cold. I have no codes, but I do have access to techstream and OBD Fusion app, so I can track engine temp, etc. The other day I popped the hood after driving a bit and felt the two hoses leading to the heater core. They were warm but not hot, so I think coolant is circulating. So either it is not circulating much (or at least not the hot coolant), or it is but the air mixer is not working right. So today I popped out the glove box and passenger foot vent and could see a cover slide back and expose the lower heater when I turned air temp to full heat...yet still barely any warmth came (some). Not sure whhether this lower heater is electric or the upper one, nor do I know how to know which was producing the little heat). I also checked techstream and it registered correct ambient and cabin air temperatures (so no temp sensor problems there). I then drove 20 minutes urban traffic and saw the engine temperature go to 200F...but still not any heat blowing out. So what should I try next? Is there certain techstream readings that would eliminate the pump and coolant thermostat being sticky? Which heater is producing that tiny bit of heat I feel? One other note- when I ran techstream on the mixer actuator it only allowed a range of 0 to 93. I could not get it to go above 93 (the intake/outtake actuators go to 256 I think). I could select up to 256, but the target and actual levels always went to 93 a second or two later. Not sure if this is normal or not.
     
  2. Eddy Connelly

    Eddy Connelly Member

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    What I can say is that when my engine reaches around 190f, I'm definitely getting decent heat. How are the coolant and oil levels?
     
  3. bisco

    bisco cookie crumbler

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    does the 3 way coolant control valve come into play here? i would think you'd get a trouble code though
     
  4. Norwich2

    Norwich2 Junior Member

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    Oil and coolant are good. I even drained and refilled both recently to be sure. Made sure to open air bleeder on coolant refill. Coolant level had dropped a bit since, so I topped it off yesterday. Still no codes. Today we had frost in a.m. and I still no hot air, even after driving 15 minutes. I also have a 2nd gen Prius and did have a P1121 code and the 3-way valve replacement fixed it. That issue is resolved though, this one on Gen 3 isn't.
     
  5. tankyuong

    tankyuong Senior Member

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    Sounds like You still have air in your system
     
  6. jack black

    jack black Active Member

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    i would check for HG failure. no heat and disappearing coolant are some of the symptoms.
     
  7. NutzAboutBolts

    NutzAboutBolts Senior Member

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    I would check the actuator like you said. You have normal coolant temp. The one that controls the cold and hot temp isn’t switching to the hot level as indicated.
     
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