1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Heater/AC Air Duct Valve Hunting

Discussion in 'Gen 2 Prius Technical Discussion' started by Hytec, Sep 24, 2010.

  1. Hytec

    Hytec New Member

    Joined:
    Aug 7, 2004
    236
    9
    0
    Location:
    MS Gulf Coast
    Vehicle:
    2005 Prius
    The heater/AC air duct valve motor hunts when my 2005 is initially powered up. By "hunting" I mean it sounds as if the valve motor was trying to open and close the valve continuously and rapidly, but never getting the valve to the limit switches which would stop the motor. This hunting stops immediately when I press the inside air (recirculate) button on the steering wheel, the motor stops hunting and the valve goes to the inside air position. Then immediately after, I can press the outside air button and the valve is transferred to the outside air position and stops with no hesitation.

    Has anyone else noticed this with a 2005, or with any Gen-II? I'm sure it's not good for the motor to hunt like this. Is there something I can do to stop this, like cleaning and lubricating the valve linkage? Or is it too difficult for a DIYer to get into the mechanism?

    Thanks for any suggestions.
     
  2. vertex

    vertex Active Member

    Joined:
    Mar 27, 2009
    672
    143
    0
    Location:
    new york
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    Sounds like the air mix servo motor postion sensor is opening in some postions. The stop postions seem ok, so only when it is trying to mix air does it have a problem. You can check this by measuring the output voltage with a meter, which should go from 1 to 4 volts smoothly as you move the vane by hand from one end to the other. You can also check it with an ohm meter. On the connector on the motor, pin 1 and pin 2 are the ends of the potentiometer, and pin 3 is the wiper.
     
  3. Hytec

    Hytec New Member

    Joined:
    Aug 7, 2004
    236
    9
    0
    Location:
    MS Gulf Coast
    Vehicle:
    2005 Prius
    Thanks, Vertex, that's helpful. However, I don't know where the servo is located, or the connector, or even how to gain access. Is there a link to documentation or a service manual for that system or area?
     
  4. vertex

    vertex Active Member

    Joined:
    Mar 27, 2009
    672
    143
    0
    Location:
    new york
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    Hytec:
    Did you figure this out?
     
  5. Hytec

    Hytec New Member

    Joined:
    Aug 7, 2004
    236
    9
    0
    Location:
    MS Gulf Coast
    Vehicle:
    2005 Prius
    Hi Vertex, unfortunately I haven't had a chance to look for the servo motor connector, though I've read that it's somewhere in the passenger side foot well area, possibly up under the dash. I hope to look for it today because my plate's kinda empty. A retirees life is s-o-o-o busy ....;)
     
  6. Hytec

    Hytec New Member

    Joined:
    Aug 7, 2004
    236
    9
    0
    Location:
    MS Gulf Coast
    Vehicle:
    2005 Prius
    OK, if the air mix servo motor connector is in the passenger compartment, it is somewhere up within the dash, behind or above the glove box. I don't figure that correcting that problem is worth disassembling the dash. On the other hand, can I gain access to that connector, or to the servo motor itself from within the engine compartment?

    Thanks
     
  7. vertex

    vertex Active Member

    Joined:
    Mar 27, 2009
    672
    143
    0
    Location:
    new york
    Vehicle:
    2018 Prius Prime
    Model:
    Prime Plus
    Sorry for not seeing your post earlier. It looks like they are on the drivers side of the console. Send me a PM with your email, and I will email you the information.
     
  8. Hytec

    Hytec New Member

    Joined:
    Aug 7, 2004
    236
    9
    0
    Location:
    MS Gulf Coast
    Vehicle:
    2005 Prius
    Thanks Vertex, unfortunately it may be a day or two for the PM. My ISP (Cableone) started converting to a new e-mail system this past Friday and as of this morning is still unable to serve customers. I'll PM you as soon as my e-mail account is stable and reliable.

    Note that I did not say "service customers" which they appear to be doing very well...in the animal husbandry sense. :mad: