Can the inverter draw current from the 12v system?

Discussion in 'Generation 1 Prius Discussion' started by RathlinPhil, Nov 9, 2020.

  1. RathlinPhil

    RathlinPhil Junior Member

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    I'm have current loss from the 12v system as soon as the car is switched to "ON" the only thing that stops the battery getting drained is pulling AM2 fuse.
    Is it known for a bad inverter to draw current from the 12v battery?
     
  2. sam spade 2

    sam spade 2 Senior Member

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    Let's see if I have this straight:
    If your foot is NOT on the brake and you push the ON button, it doesn't go all the way to the READY mode and essentially is just in ACC mode.......where it will draw from the 12 V battery and that is normal. The inverter is not active.

    If you do go to READY, which most people probably think of as "ON", then the 12 V battery should NOT be showing a net discharge.
     
  3. jerrymildred

    jerrymildred Senior Member

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    No, the inverter won't draw current from the 12V in ON (as opposed to READY). But a lot of other stuff will drain the 12V and since the car isn't in READY, the inverter & traction battery will not maintain the 12V charge. There are dire warnings in the owner's manual about this practice.
     
  4. RathlinPhil

    RathlinPhil Junior Member

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    The gen 1 doesn't have a start button. It has ACC , ON and then you turn the key a bit more to start "START" to get into ready mode. My current loss begin when put into "ON"
     
  5. jerrymildred

    jerrymildred Senior Member

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    Answer is the same. If it's not in READY, it will drain the 12V. It's not the inverter draining it; it's all the computers and other stuff on the 12V bus.
     
  6. RathlinPhil

    RathlinPhil Junior Member

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    Well something on the AM2 fuse circuit is sucking juice. The manual says this fuse is "multiport fuel infection system and hybrid vehicle immobiliser system" .
    Now......, I doubt it's the injection system,
    Has anyone heard of the immobiliser doing anything like this?
    From the forums it seems AM2 is the inverter coolant pump fuse on some models. I wonder what else is on this circuit...
     
  7. RathlinPhil

    RathlinPhil Junior Member

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    Right yeah I got you . There is going to be a certain draw with computers, relays ect..... But I'm losing to much.... It has to be a short...
     
  8. RathlinPhil

    RathlinPhil Junior Member

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    There is an audible buzz/hum inside the car when the car is switched to "ON" (not ready) It seems to be coming from either the front of the inverter or possibly the pump below, I take it that is the inverter coolant pump that one behind the passenger headlight?
     
  9. RathlinPhil

    RathlinPhil Junior Member

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    So if the inverter in not powered when car is switched to "ON" it must the pump that is on.
    If the MG starts the petrol engine with power from HV batt via the inverter does this mean the inverter only fires up when you hit "start" ?
     
  10. jerrymildred

    jerrymildred Senior Member

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    It's not a matter so much of "firing up," I think. It just doesn't have any input power from the traction battery or the MGs. You may have an issue with the inverter pump, though. I don't have experience with Gen 1, but the pump on later models does run in either ON, ACC or both. Not sure which. If you're hearing a hum from that area and it's draining the 12V fast, it's a good place to look.

    Maybe we can flag @Elektroingenieur to see if he knows. And he probably does know. ;)
     
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  11. ChapmanF

    ChapmanF Senior Member

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    Turning the key to 'start' on a Gen 1 is like pressing the button with your foot on the brake in a Gen 2. It is a signal to the HV ECU that you would like starting to happen.

    The HV ECU then looks around to make sure things are sane, and if they are, signals the system main relays in the traction battery to close, signals the inverter to, um, invert, drives the output transistors to send juice to MG1, suggests to the engine ECU that a nice 1000-or-so rpm idle would be welcomed, and poof!, you're in business.

    The Gen 1 inverter cooling pump does run whenever the key is ON.
     
  12. Josey

    Josey Member

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    I wonder whether your inverter coolant pump isn't seized up (or close to it). Those are a common failure item, and if seized up somehow would ramp up current draw. I don't know the technicals in the AM2 fuse, but your observations would fit with that.
     
  13. ChapmanF

    ChapmanF Senior Member

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    I would wonder about the pump making an audible buzz/hum if seized up though. But it should be easy enough to check, nothing more than the old look-for-reservoir-turbulence trick.
     
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  14. Josey

    Josey Member

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    Yeah. I was thinking more about it and seized made less sense than something like on its way to seized - spinning but jammed up somehow. Or even a system blockage. Anything that would put excessive load on the pump. Fortunately I haven't had to mess with my pump. But unfortunately it means I don't know how they're constructed so can't speculate on pump near-failure modes if there are any.
     
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  15. RathlinPhil

    RathlinPhil Junior Member

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    Thanks for the explanation and for helping with the pondering.... You've chimmed in a few times with advice on my gen 1 issue and I appreciate it, every person that try to help, gets me a bit further along in understanding and I think I'm getting closer to the problem.

    So the pump is running and it is it that is audible inside the vehicle when"ON" it is working, I can see slight turbulence in the reservoir, and when I unplugged it the hum stopped. It couldn't be drawing much current anyway as it is tiny as are the wires to it.
    I've starting to think there is nothing wrong with the inverter, The problem seems to be the voltage received by ECU gets too low when I hit the brake and start, the relays open and I use bad language.

    The loss increases with load increase.
     
  16. RathlinPhil

    RathlinPhil Junior Member

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    I realize not many people are driving these old wagons anymore and I get the feeling folk on the group are weary of helping amateurs muck through what are probably basic 12v problems that good technician could trace fairly easily.

    I'm a fisherman not a technician but I will perceiver and this old lady will ride again.
     
  17. sam spade 2

    sam spade 2 Senior Member

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    EXACTLY what leads you to believe that ?
    The normal load coupled with a weak battery or a bad connection can make it LOOK like too much current is being drawn when it really is not.

    Further "discussion" of your situation without you checking the battery and it's main connections first is just a waste of everybody's time.
     
  18. vvillovv

    vvillovv Senior Member

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    I've read 3 threads concerning issue, Here in the Newbie section and the techstream thread.
    Both here and the newbie section threads have a bunch of posts all trying to be helpful.
    I've been looking around to get more info on the gen1 and I started by searching for the location of the 12v - probably under the hood, but it would take me forever to dig up my gen1 pics to confirm.

    I'm not a pro either, and electical for me has been one of the three most difficult aspects to grapple with on cars, not to mention utiltiy supply.
    I've done some beginner diagrams and troubleshooting and it's a steep learning curve for me too.

    Searching gen1 ain't easy either.

    found these wiring diagrams - classic prius 2001 electrical diagrams at DuckDuckGo

    or search classic prius 2001 - thanks john1701

    between techstream, search terms and diagrams you'll find the reason.
     
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  19. ChapmanF

    ChapmanF Senior Member

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    It's in the trunk, on the left side. Prius aux batteries didn't move under the hood until Gen 4.
     
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  20. RathlinPhil

    RathlinPhil Junior Member

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    I have only now had a chance to tackle this car again, with techstream working now it reports sub code 266 along with P3125 .

    I've bought a brand new yellow top optima to keep the 12 volt police around here happy.

    code 266 = Open or GND short in inverter voltage signal circuit

    apparently these are the next steps.

    (INSPECTION PROCEDURE 1 Check for open, short and +B short in wire harness between HV ECU VB and MIVG terminals and converter & inverter assembly VB and M-GINV terminal (Seepage IN-41).

    HINT:Confirm that there is no open circuit in the wire harness. If the voltage between the HV ECU VB or MIVG terminal and body ground is always more than 5V with the ignition ON, the inverter voltage signal circuit has+B short.

    NG ? Repair or replace wire harness.

    OK? Is there DTC P3100 being output?

    YES? Check applicable DTC.

    NO? Replace converter & inverter assembly.)

    Can anyone tell me what is meant by VB? does it refer to the connector?
     
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