Intermittent Climate Control Problem

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by hngu7721, Feb 23, 2009.

  1. hngu7721

    hngu7721 Junior Member

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    The AC/fan/heater stopped working this weekend and I have no idea why.

    I've tried pushing all combination of vent controls/temp adjustments and turning AC on/off with no luck. In addition, the fan does not turn on to blow any type of air through the vents!

    however, while driving over a speed bump or backing out of a sloping driveway; the AC will kick on again as if nothing ever happened! it looks like a sudden jarring will connect whatever it is that is somehow not making a connection?

    My guess is that there's definitely an intermittent mechanical problem somewhere; but where?!?!

    Any additional thoughts or suggestions as to what I should try? Does anyone have a schematic of the climate control system?


    TIA
     
    #1 hngu7721, Feb 23, 2009
  2. firepa63

    firepa63 Former Prius Owner

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    Could be a blown fuse.
     
    #2 firepa63, Feb 23, 2009
  3. JimN

    JimN Let the games begin!

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    If it is under warranty take it to the dealer. Maybe a loose connection. If it doesn't work at all my vote is blown fuse. If it's a fuse and the replacement blows then you need to find the short & fix the real problem.
     
    #3 JimN, Feb 23, 2009
  4. hngu7721

    hngu7721 Junior Member

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    If the fuse was blown, then there shouldn't be the intermittent on and off correct? Wouldn't a blown fuse just render the climate control inoperable?

    Unfortunately, i'm 20K over my warranty

    If someone has access to the schematics, can you see if there is a relay in-line somewhere along the system?

    THanks!
     
    #4 hngu7721, Feb 23, 2009
  5. richard schumacher

    richard schumacher shortbus driver

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    Any other co-incident events: collision, installation of third-party electronics,... ?
     
    #5 richard schumacher, Feb 24, 2009
  6. jayman

    jayman Senior Member

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    I've reached my 50 MB attachment limit, so can't help much here. However, if you search around the site, I *have* posted factory schematics of the HVAC system

    When I have time, I'll try to snoop them out.
     
    #6 jayman, Feb 24, 2009
  7. hngu7721

    hngu7721 Junior Member

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    thanks for the info jayman.

    please let me know when you're able to locate the schematics!
     
    #7 hngu7721, Feb 28, 2009
  8. jayman

    jayman Senior Member

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    #8 jayman, Feb 28, 2009
  9. hngu7721

    hngu7721 Junior Member

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    Fantastic! This is extremely helpful.

    Looking forward to seeing the rest...
     
    #9 hngu7721, Feb 28, 2009
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you're serious about trying to fix this problem yourself, may I suggest that you invest $10 in techinfo.toyota.com so that you can download the electrical wiring diagram as well as the repair manual sections relevant to the problem.

    From your OP, I assume that both the MFD A/C controls and the steering wheel A/C controls are non-functional when the problem appears. My first suggestion is that you verify whether 12V power to the A/C control assembly is intermittently being lost. That assembly is hiding behind the center console below the MFD and stereo. That ECU receives power via the 15A ECU-B and the 10A A/C (HTR) fuses; both fuses are located behind the instrument panel on the driver's side. To confirm this guess you would have to set your digital voltmeter to measure voltage from the IG pin of the A/C ECU to ground; then from the +B pin of the A/C ECU to ground. See if +12VDC disappears from either pin when the problem occurs.

    If you find that voltage is present on both pins while the A/C system does not respond to the A/C controls, then I suggest removing all wiring harness connectors to the A/C ECU. Look for corrosion or any other reason for an intermittent connection, then reseat the connectors.

    If you still have an intermittent problem, then my guess is that you have a loose connection within the A/C ECU. Should you come to that conclusion, it would be easier to buy a salvage replacement unit than to figure out where that loose connection exists.
     
    #10 Patrick Wong, Mar 1, 2009
  11. jayman

    jayman Senior Member

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    If you subscribe on a Friday afternoon, TechInfo should let you have the entire weekend on a daily subscribe for $10. Getting the schematics would be helpful, keep in mind I have an '04 and have no idea how much has changed.

    The most obvious place to look is the connector at the HVAC blower. I've had them come loose or have a bad connection on a few cars/trucks in the past, so I always check that first
     
    #11 jayman, Mar 1, 2009
  12. hngu7721

    hngu7721 Junior Member

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    Patrick/jayman,

    Thank you both for the prompt suggestions and information. I've gone through the FUSE box (driver side, under steering wheel) and have confirmed that i'm getting good voltage readings at the fuse in line with the AC unit. My next guess would be to check voltage at the HVAC blower connector during failure.

    I believe I have all the info to troubleshoot the problem now, but will have to wait until the AC failure shows up again.

    THanks again for all your help!
     
    #12 hngu7721, Mar 2, 2009
  13. jayman

    jayman Senior Member

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    No worries, let us know what you uncover
     
    #13 jayman, Mar 2, 2009
  14. heffd

    heffd New Member

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    I have the same problem with my '05. My A/C would go out on me periodically and then the actual blower started to go out on me periodically. I currently leave my defroster fan on andhope that a bump in the road doesn't shut it off. I hope you keep this post updated.
    Thanks

     
    #14 heffd, Mar 4, 2009
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