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Dead 12v but still a whirring under the hood

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by oeightonenine, Jan 31, 2019.

  1. oeightonenine

    oeightonenine New Member

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    It's been very cold in the midwest these past few days. My 2007 Gen 2 is parked in an uninsulated garage. For the past 4-5 days, I noticed the red triangle would come on upon startup and quickly disappear. I decided to try the self-diagnostic (car on, hold info and turn lights on/off three times), but couldn't get it to work easily, so I gave up. My car was able to start immediately after and again about 5 hours later.

    I decided to give the diagnostic process another go today. After one round, the only instrument lights that came on were the passenger airbag and the parking button's green light flashed every 3-5 seconds. The car would not start and nothing else would turn on. I'm not sure what eventually caused the airbag and P lights to go off, but they did within minutes. Now, the cabin lights don't come on, the car doesn't respond to the key fob lock/unlock. Okay, so I need a new battery.

    BUT...I still hear the faint whirring noise under the hood. It's not a new noise. It's the same noise I hear when I start the car, drive around, park the car. Normally the noise stops after a few minutes. But it's been an hour and the whirring is still going on.

    I have several hours until someone can pick me up and take me to the store to buy a new battery. Should I be worried about another problem, too? I'm obviously curious as to the red triangle, but I hope with a new battery, it will either disappear or I will be able to run the diagnostic test.
     
    #1 oeightonenine, Jan 31, 2019
  2. Skibob

    Skibob Senior Member

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    How cold is it and what type of oil are you using? That light could be low oil pressure caused by being cold or low. Have you checked the oil level lately?

    Also starting the car and not driving it is not a good idea. You should drive the car a few miles after you start it. If you are just starting the car to see if it will run it’s hard on both batteries.
     
    #2 Skibob, Jan 31, 2019
  3. JC91006

    JC91006 Senior Member

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    I believe it's a failing brake actuator/accumulator pump you are experiencing. The pump is only suppose to run for a few seconds, but you mentioned it runs and stops within "minutes". So it's safe to say it's been leaking for a long time, it's just now not able to maintain pressure and running constantly.

    This unfortunately is an expensive and somewhat common failure on 12+ years old Prius cars.
     
    #3 JC91006, Jan 31, 2019
  4. fuzzy1

    fuzzy1 Senior Member

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    If that whirring noise normally starts the moment you open the driver door, then it likely is the brake accumulator that JC91006 mentions. And if it has been recently running for minutes, not ending within seconds before you even start the car, then it was on its way to failure even without this cold snap. And its overly long operation would be wounding your 12V battery too.
     
    #4 fuzzy1, Jan 31, 2019
  5. bisco

    bisco cookie crumbler

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    it could just be a very weak 12v causing the pump to run slowly
     
    #5 bisco, Jan 31, 2019
  6. jerrymildred

    jerrymildred Senior Member

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    A weak 12V will make the brake pump take a long time to make pressure. And it can cause other lights to come on if it's low enough. It may not be bad, though. Try putting it on a charger. If it's super-cold (like 20-30 below) you may need to take the battery to a warm place to get it to take a charge. (I haven't always lived in FL, LOL. I've been in -30F w/o wind chill a few times.) However, inability to take the cold is an early warning sign for batteries.

    But, you also may have a failing pump. I''d check the low hanging fruit first, though by making sure the 12V is up to snuff.
     
    #6 jerrymildred, Jan 31, 2019
    SFO likes this.
  7. dolj

    dolj Senior Member

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    That was my initial thought, too, reading the OP. You could try charging, but more likely you will end up replacing the 12 V battery.

    Once you have charged/replaced, see how the accumulator behaves.
     
    #7 dolj, Jan 31, 2019
    jerrymildred likes this.
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