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Climate control keeps changing the set temperature

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by 04 Prius, Aug 4, 2017.

  1. 04 Prius

    04 Prius Member

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    Hey all I have 2 questions:

    This has been going on since I bought my car 4 years ago. When I shut the car off, the next time I turn it on it seems to always want to readjust itself to be at 74*. I like to keep it @ 70 as it gets stuffy & I get sleepy @74. Is this normal?

    The second question, it keeps alternating the outdoor temperature display in Celsius & Fahrenheit every time I turn the car on, is there a way to keep it on Fahrenheit?
     
    #1 04 Prius, Aug 4, 2017
  2. bisco

    bisco cookie crumbler

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    what happens if you shut it off at 74 degrees?
     
    #2 bisco, Aug 4, 2017
  3. 04 Prius

    04 Prius Member

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    Never thought to try that......
     
    #3 04 Prius, Aug 4, 2017
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  4. drysider

    drysider Active Member

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    Is it in "Auto"? This is not a normal Gen2 action.
     
    #4 drysider, Aug 4, 2017
  5. 04 Prius

    04 Prius Member

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    Yes, it's always left in auto unless winter mornings when I need the defrost.
     
    #5 04 Prius, Aug 5, 2017
  6. 05PreeUs

    05PreeUs Senior Member

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    Not at all normal, the controller should retain the pre-set temperature unless the 12v is disconnected or it is physically changed by the operator.

    Again, not normal.

    Putting these two symptoms together, you are likely losing B+ power to the display (controller), or you may not have it at all. Check your fuses as a first step.
     
    #6 05PreeUs, Aug 5, 2017
  7. 04 Prius

    04 Prius Member

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    Fuses are good, sometimes on short trips closely spaced it'll retain it for a few trips, then randomly decide it knows better than what I want....
     
    #7 04 Prius, Aug 5, 2017
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    So if that bugs you, maybe you should replace the AC amplifier. That is the ECU which controls the HVAC system.
     
    #8 Patrick Wong, Aug 5, 2017
  9. 04 Prius

    04 Prius Member

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    It is a bit annoying, that said, I've had the car 4 yrs now & it's always done that. I could swap it with one out of my donor car, is it reasonably accessible or a major job?
     
    #9 04 Prius, Aug 7, 2017
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I believe the AC amplifier is mounted on the floor of the passenger cabin, below the radio assembly. You would need to remove the plastic trim panel that extends from the floor up to the instrument panel, for access.
     
    #10 Patrick Wong, Aug 8, 2017
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  11. 04 Prius

    04 Prius Member

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    Thank you sir! I shall check into this after I wrap up commissioning the wife's new to us car. (2006 Prius)
     
    #11 04 Prius, Aug 12, 2017
  12. 04 Prius

    04 Prius Member

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    I decided to attack this while my car was down rebuilding the HV battery, wiring looked ok, replaced the amplifier & haven't had to adjust anything since! Thanks again Patrick!
     
    #12 04 Prius, Sep 18, 2017
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  13. Jomarayprius

    Jomarayprius 2010 Prius, 2014 Prius

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    This is happening on my third Gen Prius also. 2010. Shut off the car, then at cold start up there is minimal display on the temperature control panel, then when you touch a control, like fan speed, the temperature is set to 25 C (in Canada) and you have to put it back down to the temperature you want.
    Think it would be the same fix?
     
    #13 Jomarayprius, Aug 26, 2018
  14. dolj

    dolj Senior Member

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    Hard to know, but as you have 2 Gen 3 Prii, perhaps if you ask your question over in the Gen 3 equivalent forum, the good folk more knowledge in the ways of the Gen 3 may know and be able to help you.
     
    #14 dolj, Aug 26, 2018
  15. Thakur

    Thakur New Member

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    I went through 100% identical issues. Turned out battery connection were loose. We got replacement battery from orielly autos parts and tech probably was not aware that prius requires battery connection seated really well and need tighten well
     
    #15 Thakur, May 3, 2024
  16. dolj

    dolj Senior Member

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    Prius are not special in this regard. All cars need both terminal clamps seated and tightened firmly.
     
    #16 dolj, May 4, 2024
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  17. BiomedO1

    BiomedO1 Senior Member

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    Yep,
    1. clean both posts and terminals
    2. seat and tighten terminals
    3. spray sealer over both terminals.

    Last step is optional for batteries that live in the passenger compartment of the car, since it isn't exposed to the elements as a battery under the hood is. But it should be a good idea to seal them along with ground points to prevent corrosion / bad contact.
     
    #17 BiomedO1, May 4, 2024
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