Loud droning sound from under hood during hot weather.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by co_prius_3, Jul 29, 2012.

  1. co_prius_3

    co_prius_3 Member

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    I've noticed a loud droning or fan noise coming from under the hood. It's loud enough to be heard inside the car with the hood closed. It usually happens when the car is just started and the outside temperature is in the high 90s. I assume it's one of the cooling fans, but it seems louder than one would expect. Has anyone else noticed this? I haven't tried turning the AC off to see if it is associated with that.
     
    #1 co_prius_3, Jul 29, 2012
  2. jdcollins5

    jdcollins5 Senior Member

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    It is most likely the AC. Try turning it off to verify. It is a variable frequency motor so what you are hearing is the electric switching frequencies.
     
    #2 jdcollins5, Jul 29, 2012
  3. LulzChicken

    LulzChicken Prius Enthusiast

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    It's the A/C compressor.
     
    #3 LulzChicken, Jul 29, 2012
  4. co_prius_3

    co_prius_3 Member

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    Yeah, I just tested it by turning the AC off. The droning sound stopped. It seems louder than it was when it was new, or at least I never noticed it. It shouldn't be that loud IMO. I'll have them take a look at it when I bring it in for the next oil change.
     
    #4 co_prius_3, Jul 29, 2012
  5. LulzChicken

    LulzChicken Prius Enthusiast

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    The noise usually starts loud when you first turn the AC on, but gradually gets softer. The more the AC works the louder the noise is. I wouldn't worry about it. It's more than likely normal. It seems a little loud to me too, at times.
     
    #5 LulzChicken, Jul 29, 2012
  6. jdcollins5

    jdcollins5 Senior Member

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    If the noise really bothers you, there is a customizable configuration that your Toyota dealer can change to reduce the noise. The tradeoff though is that the unit loses some efficiency.
     
    #6 jdcollins5, Jul 29, 2012
  7. co_prius_3

    co_prius_3 Member

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    Thanks. It's not so much the noise, but the concern that something was faulty. If it's normal, then I won't worry about it.

    I can always turn up the radio. ;)
     
    #7 co_prius_3, Jul 29, 2012
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  8. wls

    wls Junior Member

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    This happen to my prius too, ac compressor noise, the dealer replace my compressor unit, you should take it back to your dealer while still under warranty, this not cheap to replace dowm the road. picking up my car tomorrow.
     
    #8 wls, Jul 31, 2012
  9. co_prius_3

    co_prius_3 Member

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    I will mention it to them at the next oil change. I didn't remember it making that noise a year ago.
     
    #9 co_prius_3, Jul 31, 2012
  10. macman408

    macman408 Electron Guidance Counselor

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    One other recommendation - if you're not doing so already, try using A/C in Auto. Specifically, set the temperature to whatever level makes you comfortable, and adjust it up or down in lieu of adjusting the fan speed. If you manually set the temperature very low and the fan speed very low, it will run the compressor very hard (to reach the desired temperature) even though it's not providing much cooling (because the fan speed is set low too).
     
    #10 macman408, Jul 31, 2012
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