Need help determining cycling solenoid

Discussion in 'Generation 1 Prius Discussion' started by sandy11246, Jun 13, 2018.

  1. sandy11246

    sandy11246 Member

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    Seems to be.a relay or stepper motor. Only cycles when ICE operating or in ready. Will not appear if I just turn to key on. No CE or Triangle. Vehicle runs fine. Thought it might a pulse width signal to fuel pump. Will try to locate area tomorrow and see if I can ID the part or unit. Any ideas welcomed. Vehicle has been runing great. Thanks to all! Peace.
     
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  2. sandy11246

    sandy11246 Member

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    Checked all systems for codes and strange data indications. No codes and values seems fine. Sound seems to be coming interior from under dash or near firewall, but I'm not positive of location. I'm not even sure I have a problem but the sound something I haven't noticed before. If anyone has any ideas, please help. Right now I'm lost. I've manually cycled Evap solenoids and fuel tank with Techstream. Can't duplicate sound. Help.
     
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  3. Brian in Tucson

    Brian in Tucson Active Member

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    Turn up the radio and don't worry about it.
     
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  4. sandy11246

    sandy11246 Member

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    Brian - What do you think it is. I would fell better if I knew what was going on.
     
  5. ChapmanF

    ChapmanF Senior Member

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    There's a video attached to this thread with the sound of a noisy HVAC servo, in case it might be that.

    The video is actually attached to the thread (not hosted on a media site) ... can be downloaded, unzipped, and played.

    -Chap
     
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  6. Andyprius1

    Andyprius1 Senior Member

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    I used to know an idiot who really thought that way. I guess your commenting tongue in cheek?

    So it shouldn’t actuate until a HVAC change was made, or ignition ready?
     
    #6 Andyprius1, Jun 13, 2018
    Last edited by a moderator: Jun 18, 2018
  7. ChapmanF

    ChapmanF Senior Member

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    The HVAC dampers are positioned by servos—that is, actuators with built-in position sensor feedback. The ECU knows where it wants the position to be, so if the sensed position is different, it drives the servo toward the desired position.

    When the position sensor gets old and electrically noisy, it's as if the ECU is seeing the damper position constantly jumping around. So the ECU keeps constantly driving the actuator trying to get the position back where it should be. So no, it doesn't depend on you making any HVAC change.

    -Chap
     
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  8. sandy11246

    sandy11246 Member

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    Thanks Chap, I’ll get on it tomorrow. Don’t like things not working correctly. You guys are GREAT! If I need more assistance I’ll yell. Thanks again. It’s been running great and don’t want to lose it.
     
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  9. Andyprius1

    Andyprius1 Senior Member

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    You may actually find some play in the linkage. Fortunately I have bad hearing, so everything works perfect, I don’t even have to turn my radio up, to drown out the knocking engine.
     
  10. sandy11246

    sandy11246 Member

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    Thanks Chap for all your help as I work through our Gen1. Serviced AC door motor, now no noise. Linkage operates as it should. Vehicle is a gem, good in-town mileage and appears to get around 45+ Hwy. No real issues once I worked through the initial problems. First oil change coming up so 3000 plus since purchase. Only problem I had with motor was R&R as I'm 6'2" and 215# so getting under dash on left was a chore. No worries, got her done. Many thanks again. Maybe someday I will be able to help other with what I'm learning.
     
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  11. ChapmanF

    ChapmanF Senior Member

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  12. Andyprius1

    Andyprius1 Senior Member

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    TY You already have.
     
  13. ChapmanF

    ChapmanF Senior Member

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    I've just added this same note on my original thread:

    For future reference, the Gen 3 Prius replaced these actuators having potentiometer-style feedback with a new design using Hall-effect sensors for the feedback. So this should be a very uncommon issue in Gen 3 or later. Gen 1s and 2s are likely to experience it as they age, and as you can see, it's very easy to fix.

    The one exception might be if the air-inlet damper is the one that gets noisy. The other two servos (air mix for temperature, and outlet select) are on the easy-to-reach side of the heater case. The air inlet one is much harder to reach on the other side of the case, sandwiched between it and the blower. The dash might really have to come off to reach that one. I never had to do it (had my Gen 1 up to 230,something thousand), but it is built the same as the other two, so somebody keeping a Gen 1 or 2 super long might eventually have to deal with it.

    -Chap
     
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