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Acces to DC/DC converter without draining?

Discussion in 'Gen 2 Prius Technical Discussion' started by AlexY, Aug 26, 2020.

  1. AlexY

    AlexY Member

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    My DC/DC is draining 12V battery when car is off, confirmed it by disconnecting it's cable from this stupid fuse bar in fuse box (moron who designed it should be sued). Car is working fine, no errors in techstream, 12V in READY state is 13.8V it just draw over 1A when off.
    Before I order complete inverter assembly I would like to take a look if it is not some capacitor gone. Is it possible to lift / turn over without complete dismantling half of the car and draining cooling system?
     
    #1 AlexY, Aug 26, 2020
  2. edthefox5

    edthefox5 Senior Member

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    There not that much of a moron.

    All the power leads to the 12 volt battery are simply unclick the plug and pull it out. The lead with the fat wire is the main B +wire to the front fuse box jump point the smaller wire which is also simple unclick and pull also just hold the tab in and pull its the sensing wire to the Inverter.
    No unbolting anything to remove the 12 volt power from the car.

    The standup box to the left of the battery is full of capaioctors that are used as emergency 12 volt backup in case the 12 volt battery goes completely dead while driving there is enough 12 volt energy in that box to allow you to safely stop.

    Reports of those caps in that box going high esr from age and sucking 12 volt juice juice when off. There's your current draw not the inverter.

    You got anything and I mean anything wrong with the inverter your dash will be filled with obd alert lights.
     
    #2 edthefox5, Aug 27, 2020
  3. ChapmanF

    ChapmanF Senior Member

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    Now I am confused about which end of which cable the original poster claimed to have disconnected.
     
    #3 ChapmanF, Aug 27, 2020
  4. AlexY

    AlexY Member

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    Sorry I was not precise enough, I've disconnected 12V inverter cable from high current fuse bar. Current dropped to several mA.

    I though brake cap is connected when car is on, not all the time. Anyway no change when unplugged it. Assume inverter can't be inspected without full disassembly so going to buy used one as I'm not sure it will be repairable and car bust be fine for next week.
     
    #4 AlexY, Aug 27, 2020
    Last edited: Aug 27, 2020
  5. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Start at 1:07:45 to 1:10:30
     
    #5 JimboPalmer, Aug 27, 2020
  6. ChapmanF

    ChapmanF Senior Member

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    Was it one of the white wires (3D, 3E,or 3F here) or the black one (3M) ?

    unita.png
     
    #6 ChapmanF, Aug 27, 2020
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  7. AlexY

    AlexY Member

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    It is 3D with description DC/DC 100A on the fuse box cover.
     
    #7 AlexY, Aug 27, 2020
  8. ChapmanF

    ChapmanF Senior Member

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    3D doesn't go where you think. It's the white wire going off the right side of this page at the bottom:

    psrc.png


    and it comes in to this one at the top left:


    ps3d.png


    so you can see your DOOR, OBD, ECU-B, and a few other always-on circuits are what you disconnected. Meanwhile, you didn't disconnect your converter from the battery; that would have been 3E.

    I hope you haven't started wrenching on the converter yet.
     
    #8 ChapmanF, Aug 27, 2020
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  9. AlexY

    AlexY Member

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    Nothing removed yet. Meantime I've started studying diagram and possibly it was 3E, not sure now and don't want to remove it all again in the rain, tried to remove inverter end of 3E cable but failed as there is not enough room to release the connector's latch and push it out at the same time.
    I'm pretty sure this is inverter as some month or 2 ago 12V battery failed and in process of diagnosis I've hooked up regulated power supply and accidentally increased voltage to over 17V instead of current limit. I've got used to reversed knobs location on PSU at work. Strange thing is it exhibited issues just last week.

    Looking at the photos of interior of the DC/DC there is actually nothing that could failed, I see some red capacitors but they usually are 100V or higher rating so should survive. Seems I have to remove fuse bar again...

    Did it again, found my old (over 25 years) protek 506 multimeter have fault in high current measurement circuit causing wrong reading and excessive resistance between probes. Checked with cheap simple spare multimeter and current is fine at 20mA range.
     
    #9 AlexY, Aug 27, 2020
    Last edited: Aug 27, 2020
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