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Weird inverter temp reading

Discussion in 'Gen 2 Prius Technical Discussion' started by kens97uber171, Jul 1, 2020.

  1. kens97uber171

    kens97uber171 Active Member

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    2008 Prius
    Model:
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    Using Hybrid Assistant.
    The Inverter temp had been reporting 127f normally. With minor fluctuations. Would slowly climb during a long acceleration run.

    Noticed a new behavior.
    Now.. the normal driving around temp seems higher 140f or so.
    But what's really different is how it responds to throttle.
    When you hit it, during the acceleration surge at the very beginning, the temp climbs very fast to 185f or so.... But as you continue to accelerate the temp then goes back down.

    I had changed the coolant pump a while back as a preventative measure, that was working still no issues.
    I put that pump back in, and used a garden hose to flush the system both directions.

    Reassemble bled it.. same behavior.

    So I'm suspecting the temp sensor in the Inverter or wherever it is may have an issue.
    I wonder if a bad connection or failed sensor would be susceptible to the sudden thrust during acceleration.
    Or perhaps the bottom part of the radiator is clogged up, causing a lack of coolant flow. I did notice when I try to flush the system it seemed as though when I flushed it backwards through the inlet where the pump is it flowed pretty easily. But when I tried to put the garden hose up to the output hose from the electric pump It seemed as though it built a lot of pressure and didn't want to flow very well. After I flushed it a couple of times both directions it seemed as though this got better.

    Sorry for the long-winded description but I wanted to give as much information as possible. Do you guys have any suggestions as to where to go next? Can the inverter temperature sensor even be replaced or repaired? If it's a clogged radiator I guess I could try some flush. The coolant has always been perfectly clear I've never seen any debris or discoloration in the coolant. And when you pull the cap off the reservoir you can clearly see the coolant is flowing.

    Definitely appreciate any help or suggestions anyone could give. The car seems to be operating okay but it's just weird how the behavior has changed and of course I worry that if there is a significant blockage it could cause me to be stranded on the side of the road if it was to overheat the inverter.

    Thanks again for any help.

    Posted via the PriusChat mobile app.
     
  2. edthefox5

    edthefox5 Senior Member

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    Seen a few reports where the aluminum heat sink in the bottom of the inverter has become clogged from poor maintence. I have changed mine 3 times so far.
    Huge crisscross section of small channels. Go on you tube and look up

    Weber automotive. Find there Prius g2 teardown series there’s much discussion of the inverter and shows what I am talking about.

    Or you have a bad pump. Just cause it’s running does not me it’s ok. I would buy a new denso pump and try that. Not a aftermarket pump the real oem pump. Bleed it correctly then see how it does.

    A healthy bled correctly inverter coolant flow looks very aggressive when you look in the reservoir with car in ready. Mine looks like it’s boiling there’s so much movement. If yours is just moving a little there you go.
     
  3. edthefox5

    edthefox5 Senior Member

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    My have changed mine 3 times comment I meant I have changed the inverter coolant.

    The pump does not run perfect it’s whole life the pump pressure deteriorates over time especially if it’s on the original break in fluid and never changed nothing more abrasive than aluminum in solution that’s what kills the pump.

    Put a new pump and bleed with return hose correctly it should show very aggressive movement in the reservoir. It not after new denso pump the aluminum heat sink is clogged because the coolant was never changed till you bought the car I suspect.
     
  4. donbright

    donbright Active Member

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    On my car, (BAFX dongle + Torque app) it shows two different inverter temps, MG1 inverter temp and MG2 inverter temp, and also a Converter temp, which if i am not mistaken is the DC-DC converter. Mine don't typically fluctuate more than about 30 degrees F.

    Here is some data from my car, the first is when it was about 65F outside, the second when it was mid-90s F outside.
    newplot.png
    newplot(1).png
     
  5. donbright

    donbright Active Member

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    Now that I think about it.... the only thing in my whole data stream that goes up to 185F is the engine coolant. In fact on a day when it's mid 90s and my Inverters are about 140, my engine coolant is exactly at about 185F.
     
  6. edthefox5

    edthefox5 Senior Member

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    Nice data thank you.

    The 65 degree graph is correct that should not move much from there my
    07 with good denso pump measures that on a 90 degree day
    It’s always pretty close to 80-90 degrees below the motor.

    Only time I see it go higher is when you shut the car off the heat soak is intense as both the inverter and ice coolant share the rad
    It will go up to engine temp pretty quick. They fixed that issue in subsequent generations by putting the inverter rad in a separate box.

    I suspect on your car you have either an old pump or it has the original inverter fluid after dealer replaced pump. They don’t flush the coolant when replacing the pump. It’s not doing a good job of cooling. I suspect your mileage is poor also,
    And like most posters on this car forum no mileage listed

    I would also take the black plastic cover off the top of the rad and check the engine coolant by opening rad cap.

    Real easy to gauge the pumps effectiveness. make the car ready open the cap up on the inverter reservoir and look at it. Should be moving rippling real good likes its boiling and be a dark red color.
    Poor movement is bad pump bad, old coolant, clogged inverter cooling channels in the heatsink assy.
    You will not be able to achieve very good mileage with a hot inverter.
     
    #6 edthefox5, Aug 2, 2020
    Last edited: Aug 2, 2020
    donbright likes this.
  7. donbright

    donbright Active Member

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    @kens97uber171 i did more measuring of mine...looks like i was misreading the graph... my normal temps for the 2 inverters and converter are all about 120-130 when the ambient temp is around 90.

    anyways i was wondering are you always on flat ground or is it a lot of hills?

    the thing that puzzles me about the original problem is that it says the temp spikes during acceleration. i have looked through a lot of my data and my converter + inverter temps tend to spike when I am decelerating, not accelerating. (the above graphs show this , the attached graph is more clear)- as the power goes through the regenerative braking system.... and the HV Battery simultaneously shows large negative current indicating charge going into the HV battery. but i am mostly flat ground.

    i wonder if your system shows spikes in your hv battery current simultaneous with the temperature increase...
     

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  8. edthefox5

    edthefox5 Senior Member

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    Ken You say you see it flowing. Does it look like its boiling with really intense rippling or just gentle rippling?

    Mine looks like its at full boil. Again how many miles on the car?