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AC Compressor whine and poor MPG

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by PuckSR, Jun 14, 2015.

  1. PuckSR

    PuckSR Junior Member

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    I have had my 2011 Prius for about half a year. Lately, I noticed a louder than normal AC compressor. It is very loud, and I have driven it in hot weather before so I think I know what it normally sounds like.

    Issues:
    • Loud AC(sounds like small shop vac)
    • Intermittent cool air(measured @48 degrees). Car does not cool off for 30-40 minutes
    • Low MPG(sub 40 MPG)
    • Multiple 12V battery discharges(on a new yellowtop). They all went so low the car wouldn't start
    Attempted Fixes/Inspections:
    • Checked AC sight glass for bubbles, everything seemed normal
    • Checked battery for large current draw, everything seems fine
    • Tried to drive less aggressively, no change to MPG
    The temp is in the 90s with high humidity, so not running the AC is beginning to not be an option. When I do run without the AC, everything seems to work pretty good. I don't know if the battery issue is related to the AC issue. In fact, I have no idea what is causing the battery issue. Every time it has happened was over a relatively short period of time(>12 hours). I am willing to imagine that I am leaving a light on or something.

    I know that noises are difficult to diagnose over the internet, so my quick question is the following:
    Could a poorly performing AC compressor be putting a high load on my electrical system?
    Could poor performance be caused by an under-charged system? Missing oil? Something else?
     
    #1 PuckSR, Jun 14, 2015
    Last edited: Jun 14, 2015
  2. bisco

    bisco cookie crumbler

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    the a/c is high voltage and runs off the hybrid battery. perhaps it is shorted and pulling it down. and maybe there's nothing left to charge the 12v? but i'm just guessing.
     
    #2 bisco, Jun 14, 2015
  3. PuckSR

    PuckSR Junior Member

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    The 12V battery is just a weird thing. I check it. Everything is fine. It will be fine for a month. Then it tanks over night. No lights are on, but I literally have to pull the post, because the current draw from the system is too high to allow me to start the car.
     
    #3 PuckSR, Jun 14, 2015
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    Can you elaborate? FWIW, the Repair Manual says you shouldn't see bubbles when the compressor's running, then just a swirl of bubbles as it shuts down. I'm not sure I completely agree with that, I've always found (on cars in the past):

    When compressor is running a few stray bubbles whipping by are normal. Also reassuring, that you're not actually looking at nothing, air. So yeah, a few bubbles, just enough to confirm there's something in there, then a swirl of bubbles as it shuts down, would seem normal to me.
     

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    #4 Mendel Leisk, Jun 14, 2015
  5. bisco

    bisco cookie crumbler

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    there are some compressor noise threads here, perhaps they might be of help.
     
    #5 bisco, Jun 14, 2015
  6. PuckSR

    PuckSR Junior Member

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    Sorry, typo on my part. Everything seemed normal.
     
    #6 PuckSR, Jun 14, 2015
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  7. bisco

    bisco cookie crumbler

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    just a warning if you decide to take it somewhere, most a/c shapes don't have the expertise do repair an electric air conditioner, but will be happy to try and take your money anyway.
     
    #7 bisco, Jun 14, 2015
  8. PuckSR

    PuckSR Junior Member

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    Yeah. Problem is most of them are just people saying "is it supposed to sound like this?".
    I know what it sounds like, this is a bit noisier. Trying to figure out if it is linked to my poor MPG. Also, if any HVAC experts are in the house try to determine if it is a failing pump or possibly something else. If it is failing, I should run the sucker into the ground(since the only solution is replacement). If it isn't failing and the excess noise is related to some other problem, then I should fix that problem.

    I did search the forums for this problem before posting. All I could find was conversations about the noisy compressor. I couldn't find any threads about a similar issue. If you know of one, please point me towards it.
     
    #8 PuckSR, Jun 14, 2015
  9. bisco

    bisco cookie crumbler

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    i'm sorry, i don't, but i do recall at least one who replaced it with a rebuilt or salvage because the noise was so bad. you're right, most are just 'my a/c is noisy, is that okay'.
     
    #9 bisco, Jun 14, 2015
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